Saccharomyces cerevisiae Kre5p is important for the biosynthesis of beta-1,6-glucan, which is required for proper cell wall assembly and architecture. A functional and cell biological analysis of Kre5p was conducted to further elucidate its role in beta-1,6-glucan synthesis. Kre5p was found to be a primarily soluble N-glycoprotein of ∼200 kD that localizes to the endoplasmic reticulum. Observation of Kre5p-deficient cells reveals a severe cell wall morphological defect, and kre5Delta cells were shown to have only residual levels of beta-1,6-glucan. KRE6 was identified as a multicopy suppressor of a temperature-sensitive kre5 allele, suggesting these proteins participate in a common pathway. An analysis of truncated versions of Kre5p indicates that it may have two independent, essential activities, or that it functions in a homodimeric state. Finally, Candida albicans KRE5 was shown to partially restore growth to kre5Delta cells, suggesting it has a function similar to that of the S. cerevisiae protein.

Cell wall loosening and degradation are important processes in major stages of plant development including fruit ripening. Three main mechanisms have been proposed to contribute towards cell wall polysaccharide degradation in vivo: enzymic hydrolysis by endopolygalacturonase (EPG), enzymic elimination by pectate lyase (PL), and non-enzymic scission by hydroxyl radicals (•OH). However, little idea as to which of these three mechanisms predominates in homogalacturonan degradation especially during fruit ripening. This study presents an attempt to discover the respective contribution of those three mechanisms of attack. The strategy used to achieve the objective of this study was to identify and measure homogalacturonan molecules that exhibit symptoms of each mechanism of attack. A method that was developed in this study is a fluorescent labelling method mainly to study the •OH attack on pectic polysaccharides. This labelling method is based on the ability of 2-aminoacridone (2-AMAC) to reductively aminate oxo groups of sugar moieties followed by exhaustive digestion with Driselase. In a model in-vitro experiment, the developed novel fluorescent labelling method, when applied to homogalacturonan, that had been attacked by •OH (Fenton reagent), produced at least three fluorescent ‘fingerprint’ compounds, separable by high-voltage paper electrophoresis (HVPE) based on their charge/mass properties at pH 6.5 and also by high pressure liquid chromatography (HPLC) on a C18 column with a fluorescence detector at λem= 520 nm. These fingerprint compounds include: a monomer, 1A*; a dimer, 2A*; and an unidentified compound, X*. In-vivo application with alcoholinsoluble residue (AIR) of seven species of fruit (pear, mango, banana, apple, avocado, strawberry and strawberry tree fruit) at three stages of softening produced at least two fluorescent fingerprint compounds: a monomer, 1AF and a dimer, 2AF. XF, an interesting compound found in a few samples in in-vivo experiments, showed electrophoretic mobility similar to X*; however, the retention time of this compound on HPLC did not agree with that of X*. 2AF was suggested to be exclusive evidence for •OH attack in vivo while 1AF was suggested to be a useful evidence not only to reveal •OH attack but also to reveal EPG and PL attack on pectic polysaccharides during fruit softening. HVPE and HPLC results showed an increasing pattern of 2AF in mango, banana, avocado and strawberry tree fruit, which indicated progressive •OH attack on pectic polysaccharides during the softening process. There was no clear evidence of 2AF at any stage of softening in apple and strawberry, which may suggest that fruit softening in apple and strawberry was not associated with •OH attack. On the other hand, HVPE analysis of 1AF showed and increasing pattern in pear, mango, banana, avocado and strawberry tree fruit, which may indicate EPG, PL and/or •OH attack during fruit softening. Production of these fluorescent fingerprint compounds provides good evidence for •OH attack on pectic polysaccharides, and has the potential to give useful information for EPG and PL attack in vivo.

x, 153, xxviii leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1975

v, 132 p. leaves : photos., graphs, tables ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Biochemistry, University of Adelaide, 1978

x, 153, xxviii leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1975

Thesis (Ph.D.) -- University of Adelaide, Dept. of Microbiology, 1975.

Thesis (Ph.D.)--Dept. of Biochemistry, University of Adelaide, 1978.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 177-190). Also available via the Internet.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 23, 2010) Includes bibliographical references (p. 55-61)

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 238-266). Also available in electronic version. Access restricted to campus users.