No description available.

A demanda por carne de frango vem crescendo globalmente, assim como as exigências com relação à qualidade microbiológica do produto final. Associa-se a frequência de Campylobacter spp. em aves às enterites em humanos. O principal reservatório do agente é o trato digestivo de animais de diversas espécies, como aves de corte. Campylobacter spp. possui ampla diversidade genotípica e fenotípica, e apresentam diversos mecanismos de virulência para se aderir e colonizar o epitélio intestinal no hospedeiro. Apesar de o controle sanitário e biossegurança implementados nas granjas refletirem na redução de contaminação das carcaças no matadouro-frigorífico, esses procedimentos não eliminam o Campylobacter completamente das aves, podendo comprometer a qualidade microbiológica do produto final e propiciar casos de toxinfecção de origem alimentar aos consumidores. Esse trabalho tem como objetivo verificar a ocorrência de seis genes de virulência de Campylobacter jejuni em amostras de carcaças de frango e em casos de campilobacteriose em humanos. Foram avaliadas 50 amostras de C. jejuni, das quais 25 eram de origem aviária, provenientes da coleção do Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), e 25 eram de origem humana, cedidas pela Fundação Oswaldo Cruz (FIOCRUZ). A técnica de reação em cadeia da polimerase (PCR) foi utilizada para detecção dos genes iam, flaA, cdtA, cdtB, cdtC e wlaN. Das amostras analisadas, 92% (23/25) de origem humana e 88% (22/25) de origem aviária foram positivas para o gene cdtB, 44% (11/25) de origem humana e 84% (21/25) de origem aviária para o gene cdtA; 20% (5/25) de origem humana e 80% (20/25) de origem aviária para o gene flaA; 48% (12/25) de origem humana e 76% (19/25) de origem aviária para o gene cdtC; 16% (4/25) de origem aviária para o gene wlaN e 12% (3/25) de origem humana e 4% (1/25) de origem aviária foram positivas para o gene iam. Em nenhuma das amostras pesquisadas de origem humana (0/25) foi observado o gene wlaN. Com este trabalho concluiu-se que os genes pesquisados podem estar presentes em cepas de C. jejuni provenientes de carne de frango e nas cepas isoladas de casos de infecção alimentar em humanos. Ainda assim, conforme os resultados apresentados, o gene cdtB teve maior frequência nas amostras provenientes de origem humana e aviária. / The demand for poultry meat has increased globally, as well as the microbiologic requirements of the final product. The frequency of Campylobacter spp. in poultry meat has been related to enteritis in humans. The digestive tract of several animals’ species, as poultries, is the main reservatory of the agent. Campylobacter spp. has a wide genotypic and phenotypic diversity, and, in addition to that, it presents several virulence factors which allow to adhere and colonize the intestinal epithelium of the host. Although good hygienic and biosecurity practices employed at poultry farms help to reduce the carcass contamination, these procedures do not completely eliminate Campylobacter spp. at the slaughterhouses and it may affect the microbiologic quality of the final product, which may cause alimentary toxinfection cases. This study aims to verify the occurrence of six virulence genes of Campylobacter jejuni from poultry carcasses samples and campylobacteriosis cases in humans. 50 samples of C. jejuni were evaluated, of which 25 were originated from poultry collected at the Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), and 25 were originated from human samples of the Fundação Oswaldo Cruz (FIOCRUZ). Polymerase chain reaction (PCR) technique was employed to detect the following genes: iam, flaA, cdtA, cdtB, cdtC and wlaN. In the samples analyzed, 92% (23/25) from human origin and 88% (22/25) from poultry for cdtB gene; 44% (11/25) from human origin and 84% (21/25) from poultry for cdtA gene; 20% (5/25) from human origin and 80% (20/25) from poultry for flaA gene; 48% (12/25) from human origin and 76% (19/25) from poultry for cdtC gene; 16% (4/25) from poultry for wlaN and gene 12% (3/25) from human origin and 4% (1/25) from poultry were positive for iam gene. This study concludes that the researched genes may be present in Campylobacter from poultry meat origin and from isolates of human cases of alimentary toxinfection. However, according to the results found, the cdtB gene had a higher frequency in samples of human and avian origin.

No description available.

Das thermophile Bakterium Campylobacter jejuni gehört weltweit zu den häufigsten Erregern bakterieller Gastroenteritiden beim Menschen. Der Erreger wird hauptsächlich durch kreuzkontaminierte Lebensmittel, zumeist ausgehend von Geflügelprodukten, übertragen. Aufgrund seines weiten Wirtsspektrums weist C. jejuni eine hohe genetische Vielfalt unter seinen Isolaten auf. Mit dem Ziel herauszufinden, ob das Auftreten spezifischer Markergene mit bestimmten klonalen Komplexen korreliert, wurden im Rahmen dieser Arbeit 266 C. jejuni-Isolate unterschiedlicher Herkunft (Mensch, Rind, Huhn, Pute) molekularbiologisch auf das Vorhandensein von zehn Virulenz-assoziierten Faktoren: cj1321-1326 (ein sechs Gen umfassender Komplex zur Flagellin-O-Glykolisierung), ciaB (Campylobacter-Invasions-Antigen B), cdtB (cytolethales distendierendes Toxin, CDT) Untereinheit B, fucP (L-Fucose-Permease), cj0178/cj0755 (Eisentransportprotein), ceuE (Enterochelin bindendes Protein), pldA (Phospholipase A der äußeren Membran) und cstII/cstIII (Lipooligosaccharid-Sialyltransferase) untersucht. In einer vorrangegangen Studie von ZAUTNER et al. 2011 wurden bereits 266 C. jejuni-Isolate durch Kombination von MLST und den sechs genetischen Metabolismus-assoziierten Markern: ansB (periplasmatische Asparaginase), dmsA (Untereinheit A der Dimethyl-sulfoxid-Oxidoreduktase), ggt (γ-Glutamyl-Transpeptidase), cj1585c (Oxidoreduktase), cjj811-76-1367/71 (Serin-Protease) und tlp7m+c (transducer-like Protein 7 (Ameiseisäure-spezifische Chemotaxisrezeptor), Heterodimer aus Cj0951c und Cj0952c) in sechs Gruppen unterteilt. Zur Konkretisierung dieser bestehenden Gruppendefinitionen und zur Identifikation der Gruppen mit dem höchsten gesundheitsgefährdenden Potential wurden dieselben 266 Isolate nun weiter charakterisiert. Vor allem die genetischen Marker cj1321-1326; fucP; cj0178 und cj0755 sind weitestgehend miteinander assoziiert und splitten die Testpopulation in 2 Haupt- und 7 Untergruppen und bestätigen damit die alte Gruppendefinition. Abgesehen vom Virulenz-assoziierten Marker pldA zeigen alle ermittelten genetischen Marker signifikante Unterschiede unter den verschiedenen MLST-Sequenztypen. Basierend auf den Daten der Arbeit konnte ein Biotyp von C. jejuni-Isolaten, der durch die Präsenz von ansB, dmsA, ggt und die Absenz von cj1321-1326; fucP; cj0178, cj0755, cj1365c, cj1585c sowie cstII/cstIII charakterisiert ist, bestimmt werden. Isolate dieser Gruppe gehören hauptsächlich den MLST-CC 22, 42, 45, 283 an und sind eher an eine Persistenz in der Umwelt-adaptiert. Zum Wachstum nutzen die Stämme dieser Gruppe einen erweiterten Aminosäurestoffwechsel sowie einen alternativen anaeroben Stoffwechselweg (dmsA- positiv). Hingegen kann aufgrund des fehlenden fucP keine L-Fucose verstoffwechselt werden. Außerdem sind die Stämme dieser Gruppe toleranter gegen oxidativen Stress und besser frostbeständig. Die jahreszeitliche Prävalenz ist am stärksten im Frühsommer. Dieser Umwelt- aber schlechter Wirts-adaptierte Biotyp wird mit mehr Campylobacteriosen beim Menschen in Verbindung gebracht, ist häufiger mit blutigen Stühlen und Hospitalisierungen assoziiert und ist somit hochgradiger virulent für den Menschen. Im Gegensatz dazu ist die zweite Hauptgruppe stärker an tierische Wirte, insbesondere Säuger, adaptiert und in der Lage, L-Fucose aus Mucosa oder Milch zu metabolisieren. Isolate dieses Biotyps tolerieren für C. jejuni extreme Temperaturen besser und zeigen eine relativ gleichmäßige Prävalenz im Jahresverlauf. Alle fünf bekannten C. jejuni-Eisentransportsysteme sind detektierbar, ebenso die Marker cj1321-1326, cj1365c, cj1585c und cstII und/oder cstIII. Die vorherrschenden MLST-CC sind CC 21, 48, 61 und 20. Dieser besser Wirts-adaptierte Biotyp wird mit weniger schweren Campylobacteriosen in Zusammenhang gebracht. Alle anderen Gruppen stellen einen sukzessiven evolutionären Übergang an Markergen-Kombinationen zwischen diesen beiden Hauptgruppen dar.

A demanda por carne de frango vem crescendo globalmente, assim como as exigências com relação à qualidade microbiológica do produto final. Associa-se a frequência de Campylobacter spp. em aves às enterites em humanos. O principal reservatório do agente é o trato digestivo de animais de diversas espécies, como aves de corte. Campylobacter spp. possui ampla diversidade genotípica e fenotípica, e apresentam diversos mecanismos de virulência para se aderir e colonizar o epitélio intestinal no hospedeiro. Apesar de o controle sanitário e biossegurança implementados nas granjas refletirem na redução de contaminação das carcaças no matadouro-frigorífico, esses procedimentos não eliminam o Campylobacter completamente das aves, podendo comprometer a qualidade microbiológica do produto final e propiciar casos de toxinfecção de origem alimentar aos consumidores. Esse trabalho tem como objetivo verificar a ocorrência de seis genes de virulência de Campylobacter jejuni em amostras de carcaças de frango e em casos de campilobacteriose em humanos. Foram avaliadas 50 amostras de C. jejuni, das quais 25 eram de origem aviária, provenientes da coleção do Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), e 25 eram de origem humana, cedidas pela Fundação Oswaldo Cruz (FIOCRUZ). A técnica de reação em cadeia da polimerase (PCR) foi utilizada para detecção dos genes iam, flaA, cdtA, cdtB, cdtC e wlaN. Das amostras analisadas, 92% (23/25) de origem humana e 88% (22/25) de origem aviária foram positivas para o gene cdtB, 44% (11/25) de origem humana e 84% (21/25) de origem aviária para o gene cdtA; 20% (5/25) de origem humana e 80% (20/25) de origem aviária para o gene flaA; 48% (12/25) de origem humana e 76% (19/25) de origem aviária para o gene cdtC; 16% (4/25) de origem aviária para o gene wlaN e 12% (3/25) de origem humana e 4% (1/25) de origem aviária foram positivas para o gene iam. Em nenhuma das amostras pesquisadas de origem humana (0/25) foi observado o gene wlaN. Com este trabalho concluiu-se que os genes pesquisados podem estar presentes em cepas de C. jejuni provenientes de carne de frango e nas cepas isoladas de casos de infecção alimentar em humanos. Ainda assim, conforme os resultados apresentados, o gene cdtB teve maior frequência nas amostras provenientes de origem humana e aviária. / The demand for poultry meat has increased globally, as well as the microbiologic requirements of the final product. The frequency of Campylobacter spp. in poultry meat has been related to enteritis in humans. The digestive tract of several animals’ species, as poultries, is the main reservatory of the agent. Campylobacter spp. has a wide genotypic and phenotypic diversity, and, in addition to that, it presents several virulence factors which allow to adhere and colonize the intestinal epithelium of the host. Although good hygienic and biosecurity practices employed at poultry farms help to reduce the carcass contamination, these procedures do not completely eliminate Campylobacter spp. at the slaughterhouses and it may affect the microbiologic quality of the final product, which may cause alimentary toxinfection cases. This study aims to verify the occurrence of six virulence genes of Campylobacter jejuni from poultry carcasses samples and campylobacteriosis cases in humans. 50 samples of C. jejuni were evaluated, of which 25 were originated from poultry collected at the Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), and 25 were originated from human samples of the Fundação Oswaldo Cruz (FIOCRUZ). Polymerase chain reaction (PCR) technique was employed to detect the following genes: iam, flaA, cdtA, cdtB, cdtC and wlaN. In the samples analyzed, 92% (23/25) from human origin and 88% (22/25) from poultry for cdtB gene; 44% (11/25) from human origin and 84% (21/25) from poultry for cdtA gene; 20% (5/25) from human origin and 80% (20/25) from poultry for flaA gene; 48% (12/25) from human origin and 76% (19/25) from poultry for cdtC gene; 16% (4/25) from poultry for wlaN and gene 12% (3/25) from human origin and 4% (1/25) from poultry were positive for iam gene. This study concludes that the researched genes may be present in Campylobacter from poultry meat origin and from isolates of human cases of alimentary toxinfection. However, according to the results found, the cdtB gene had a higher frequency in samples of human and avian origin.

Campylobacteriosis, in the current days, is recognized as the major cause of foodborne illness in many developed and developing countries. Among the Campylobacter species responsable for the infections, C. jejuni is responsable for 75% of the cases of human campilobacteriosis, as for it, it s considered as the major species involved on the registered cases. In this work, two experiments were conduced. In the first, the presence of C. jejuni and Campylobacter spp. in poultry farms of Rio Grande do Sul State in Brazil was investigated. Epidemiological data was obtained with the person encharged by the farms, and the data obtained was corelated with the levels of contamination of each property. In the second experiment, we investigated the contamination of cicken meat and giblets adquired in supermarkets in Santa Maria city of C. jejuni as well as the freezing effect on the contamination levels in this samples. For the first trial, 280 cloacal swabs were collected from four poultry farms. In the second experiment, 9 samples of heart, liver, gizzard and drumette, tottalizing 36 samples collected. A portion of each sample was processed freshly, while the rest was freezed (-18ºC) for 7 days before it s processing. In the first trial, 147 samples (52,5%) were positive for C. jejuni and another 31 (11,07%) were identified as Campylobacter spp. The data analysis revealed correlaction beetwen the number of birds kept in de farms (p=0,05), the age of the poultry (p=0,05) and the gender (p=0,03), as female was more infected than males. In the second experiment, isolation of C. jejuni was achieved in 7 heart (77,7%), 8 liver (88,8%), 4 gizzard (44,4%) and 3 drumette (33,3%) fresh samples, corresponding to 61,1% of total samples. After freezing storage, in only 3 samples (two liver and one heart) C. jejuni was isolated (8,3%). The data obtained allowed us to conclude that C. jejuni is widely spread in poultry farms os Rio Grande do Sul state, so, improve the control procedures for Compylobacter species on the poultry fars is needed. The chicken cuts obtained from supermarkets in Santa Maria city are also higly contaminated by C. jejuni, however, freezing storage for seven days can drastically reduce the contamination levels of chicken cuts, improoving food safety, althoght, this procedure do not eliminate completely C. jejuni from de cuts analized, and the correct manipullation is needed to eliminate the risk of infeccion from poultry meat sources . / A campilobacteriose, atualmente, é reconhecida como sendo a causa mais freqüente de infecção de origem alimentar em seres humanos. Dentre as espécies responsáveis pela infecção, Campylobacter jejuni responde por cerca de 75% dos casos de campilobacteriose humana, sendo considerada a principal espécie envolvida nos casos registrados. Este trabalho é composto de dois experimentos. No primeiro avaliou-se a ocorrência de C. jejuni em granjas avícolas no estado do Rio Grande do Sul, correlacionando os índices de contaminação detectados com dados epidemiológicos obtidos através de entrevista com o responsável pela granja. Foram coletados 280 swabs cloacais oriundos de quatro granjas avícolas do Rio Grande do Sul. No segundo experimento, foram adquiridos em supermercados de Santa Maria, 9 amostras frescas de fígado, coração, moela e drumete, totalizando 36 amostras. Foi realizado o processamento de um fragmento de 25g de cada amostra fresca, sendo o restante congelado à -18ºC durante sete dias, sendo as amostras, após este período novamente analisadas. No primeiro experimento, foram obtidas 147 amostras (52,5%) positivas para C. jejuni e 31 amostras (11,07%) identificadas como Campylobacter spp. A análise dos dados revelou existir influência dos índices de contaminação mais elevados com o número de aves alojadas (p=0,05), tempo de alojamento (p=0,05) e sexo (p=0,05), sendo as fêmeas mais acometidas que os machos. No segundo experimento, realizou-se o isolamento em 7 (77,7%) amostras frescas de coração, 8 (88,8%) de fígado, 4 (44,4%) de moela e 3 (33,3%) de drumete, correspondendo a 61,1% das amostras frescas analisadas. Após o congelamento, em apenas três amostras (8,3%) foi obtido o isolamento de C. jejuni, sendo duas amostras de fígado e uma de coração. Os dados obtidos permitem concluir que C. jejuni está amplamente difundido na avicultura industrial do Rio Grande do Sul, sendo necessário ampliar os esforços para redução deste patógeno nos plantéis avícolas. Os cortes de frango adquiridos em supermercados na cidade de Santa Maria apresentam índices de contaminação elevados por C. jejuni, contudo o congelamento por 7 dias é capaz de reduzir consideravelmente os índices de contaminação, porém, não eliminando completamente C. jejuni dos cortes congelados, assim, a manipulação adequada da carne de frango continua sendo essencial para assegurar a eliminação de C. jejuni dos alimentos contendo carne de frango em suas preparações.

A demanda por carne de frango vem crescendo globalmente, assim como as exigências com relação à qualidade microbiológica do produto final. Associa-se a frequência de Campylobacter spp. em aves às enterites em humanos. O principal reservatório do agente é o trato digestivo de animais de diversas espécies, como aves de corte. Campylobacter spp. possui ampla diversidade genotípica e fenotípica, e apresentam diversos mecanismos de virulência para se aderir e colonizar o epitélio intestinal no hospedeiro. Apesar de o controle sanitário e biossegurança implementados nas granjas refletirem na redução de contaminação das carcaças no matadouro-frigorífico, esses procedimentos não eliminam o Campylobacter completamente das aves, podendo comprometer a qualidade microbiológica do produto final e propiciar casos de toxinfecção de origem alimentar aos consumidores. Esse trabalho tem como objetivo verificar a ocorrência de seis genes de virulência de Campylobacter jejuni em amostras de carcaças de frango e em casos de campilobacteriose em humanos. Foram avaliadas 50 amostras de C. jejuni, das quais 25 eram de origem aviária, provenientes da coleção do Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), e 25 eram de origem humana, cedidas pela Fundação Oswaldo Cruz (FIOCRUZ). A técnica de reação em cadeia da polimerase (PCR) foi utilizada para detecção dos genes iam, flaA, cdtA, cdtB, cdtC e wlaN. Das amostras analisadas, 92% (23/25) de origem humana e 88% (22/25) de origem aviária foram positivas para o gene cdtB, 44% (11/25) de origem humana e 84% (21/25) de origem aviária para o gene cdtA; 20% (5/25) de origem humana e 80% (20/25) de origem aviária para o gene flaA; 48% (12/25) de origem humana e 76% (19/25) de origem aviária para o gene cdtC; 16% (4/25) de origem aviária para o gene wlaN e 12% (3/25) de origem humana e 4% (1/25) de origem aviária foram positivas para o gene iam. Em nenhuma das amostras pesquisadas de origem humana (0/25) foi observado o gene wlaN. Com este trabalho concluiu-se que os genes pesquisados podem estar presentes em cepas de C. jejuni provenientes de carne de frango e nas cepas isoladas de casos de infecção alimentar em humanos. Ainda assim, conforme os resultados apresentados, o gene cdtB teve maior frequência nas amostras provenientes de origem humana e aviária. / The demand for poultry meat has increased globally, as well as the microbiologic requirements of the final product. The frequency of Campylobacter spp. in poultry meat has been related to enteritis in humans. The digestive tract of several animals’ species, as poultries, is the main reservatory of the agent. Campylobacter spp. has a wide genotypic and phenotypic diversity, and, in addition to that, it presents several virulence factors which allow to adhere and colonize the intestinal epithelium of the host. Although good hygienic and biosecurity practices employed at poultry farms help to reduce the carcass contamination, these procedures do not completely eliminate Campylobacter spp. at the slaughterhouses and it may affect the microbiologic quality of the final product, which may cause alimentary toxinfection cases. This study aims to verify the occurrence of six virulence genes of Campylobacter jejuni from poultry carcasses samples and campylobacteriosis cases in humans. 50 samples of C. jejuni were evaluated, of which 25 were originated from poultry collected at the Centro de Diagnóstico e Pesquisa em Patologia Aviária (CDPA - UFRGS), and 25 were originated from human samples of the Fundação Oswaldo Cruz (FIOCRUZ). Polymerase chain reaction (PCR) technique was employed to detect the following genes: iam, flaA, cdtA, cdtB, cdtC and wlaN. In the samples analyzed, 92% (23/25) from human origin and 88% (22/25) from poultry for cdtB gene; 44% (11/25) from human origin and 84% (21/25) from poultry for cdtA gene; 20% (5/25) from human origin and 80% (20/25) from poultry for flaA gene; 48% (12/25) from human origin and 76% (19/25) from poultry for cdtC gene; 16% (4/25) from poultry for wlaN and gene 12% (3/25) from human origin and 4% (1/25) from poultry were positive for iam gene. This study concludes that the researched genes may be present in Campylobacter from poultry meat origin and from isolates of human cases of alimentary toxinfection. However, according to the results found, the cdtB gene had a higher frequency in samples of human and avian origin.

No description available.

No description available.

Dihydrodipicolinate Synthase (EC 4.3.3.7; DHDPS), the product of the dapA gene, is an enzyme that catalyzes the condensation of pyruvate and S-aspartate-β-semialdehyde (ASA) into dihydrodipicolinate via an unstable heterocyclic intermediate, (4S)-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinic acid. DHDPS catalyzes the first committed step in the biosynthesis of ʟ-lysine and meso-diaminopimelate; each of which is a necessary cross-linking component between peptidoglycan heteropolysacharide chains of bacterial cell walls. Therefore, strong inhibition of DHDPS would result in disruption of meso-diaminopimelate and ʟ-lysine biosynthesis in bacteria leading to decreased bacterial growth and cell lysis. Much attention has been given to targeting the active site for inhibition; however DHDPS is subject to natural feedback inhibition by ʟ-lysine at an allosteric site. In DHDPS from Campylobacter jejuni ʟ-lysine is known to act as a partial uncompetitive inhibitor with respect to pyruvate and a partial mixed inhibitor with respect to ASA. Little is known about how the protein structure facilitates the natural inhibition mechanism and mode of allosteric signal transduction. This work presents ten high resolution crystal structures of Cj-DHDPS and the mutant Y110F-DHDPS with various substrates and inhibitors, including the first reported structure of DHDPS with ASA bound to the active site. As a body of work these structures reveal residues and conformational changes which contribute to the inhibition of the enzyme. Understanding these structure function relationships will be valuable for the design of future antibiotic lead compounds. When an inhibitor binds to the allosteric site there is meaningful shrinkage in the solvent accessible volume between 33% and 49% proportional to the strength of inhibition. Meanwhile at the active site the solvent accessible volume increases between 5% and 35% proportional to the strength of inhibition. Furthermore, inhibitor binding at the allosteric site consistently alters the distance between hydroxyls of the catalytic triad (Y137-T47-Y111') which is likely to affect local pKa's. Changes in active site volume and modification of the catalytic triad would inhibit the enzyme during the binding and condensation of ASA. The residues H56, E88, R60 form a network of hydrogen bonds to close the allosteric site around the inhibitor and act as a lid. Comparison of ʟ-lysine and bislysine bound to wt-DHDPS and Y110F-DHDPS indicates that enhanced inhibition of bislysine is most likely due to increased binding strength rather than altering the mechanism of inhibition. When ASA binds to the active site the network of hydrogen bonds among H56, E88 and R60 is disrupted and the solvent accessible volume of the allosteric site expands by 46%. This observation provides some explanation for the reduced affinity of ʟ-lysine in high ASA concentrations. ʟ-Lysine, but not other inhibitors, is found to induce dynamic domain movements in the wt-DHDPS. These domain movements do not appear to be essential to the inhibition of the enzyme but may play a role in cooperativity between monomers or governing protein dynamics. The moving domain connects the allosteric site to the dimer-dimer interface. Several residues at the weak dimer interface have been identified as potentially involved in dimer-dimer communication including: I172, D173, V176, I194, Y196, S200, N201, K234, D238, Y241, N242 and K245. These residues are not among any previously identified as important for formation of the quaternary structure.