By determining the Calpha and Cbeta chemical shift of P2 and its relaxation properties, together with secondary structure prediction, P2 was found to have an N-terminal 4-helices structural domain and a C-terminal unstructured coil. / P2 was found to interact with P1, forming heterodimer and with P2, forming homodimer. It was found that dimerization is carried out by their N-terminal, forming NTD-P1/NTD-P2 heterodimer and NTD-P2 homodimer. / Ribosome is the organelle responsible for protein synthesis and it was suggested that P-proteins located at the lateral stalk are involved in this process. Until now, structure of any P-protein is still not known although crystal structure of ribosome was solved. In order to know more about the biological role of P-proteins, structural characterization was carried out on human ribosomal protein P2. / The C-terminal tail which is conserved among P0, P1 and P2 of various species was found to interact with ribosome inactivating protein (TCS). This helps delivering TCS to its RNA substrate and carrying out its N-glycosidase activity. It was also found that TCS and EF2 are close in space suggesting that binding of TCS to P-proteins may hinder the association of EF2 to P-protein, thus inhibiting protein translation. / The solution structure of NTD-P2 homodimer was solved. It has 8 helices, 4 from each monomer. The surface is hydrophilic and the core is hydrophobic with a hydrophobic dimeric interface. By circular dicroism measurement, structural alignment and secondary structure prediction, we hypothesize that the dimerization mode of NTD-P1/NTD-P2 heterocomplex should be similar to NTD-P2 homodimer. Therefore, homology modeling was used to model the structure of NTD-P1/NTD-P2 using NTD-P2 as template. Interestingly, there is a small exposed hydrophobic patch on NTD-P1 which is lack in NTD-P2. This exposed hydrophobic patch may be the potential P0 binding site, forming P0(P1/P2)2 complex. Moreover, this exposed hydrophobic pocket is smaller than that of prokaryotic counterpart, thus providing insight in ribosome assembly and regulation in protein translation. / Lee, Ka Ming. / Advisers: K. B. Wong; P. C. Shaw. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0096. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 121-129). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Adiponectin, a hormone that homo-oligomerizes into trimer, hexamer, or higher molecular weight (HMW) species, is involved in maintaining insulin sensitivity in muscle and liver. Interestingly, its functions appear to be oligomer-specific. Recent data suggest that HMW levels are decreased in obesity and insulin resistance, although, the cause for this decrease is not known. Impaired assembly to the octadecamer represents one possible reason for decreased HMW adiponectin in insulin resistance and type 2 diabetes, but mechanisms by which HMW adiponectin assembles are unknown. This dissertation discusses the progress that we have made regarding formation of HMW adiponectin in vitro.I found that disulfide bonds are important in the assembly process to octadecameric adiponectin, but are not required for stability of the octadecamer itself. We showed that hydrogen peroxide accelerated oligomerization to the octadecamer through formation of disulfide bonds, while alkylation of the cysteines led to inhibition of both oligomerization and disulfide bond formation. Using comparative native/denaturing polyacrylamide gel electrophoresis (PAGE), dynamic light scattering, and tandem mass spectrometry, we demonstrated that octadecamer is stable in the absence of disulfide bonds by using multiple biochemical and biophysical assays. In addition, oxidized adiponectin oligomerizes to octadecamer far slower than reduced adiponectin. To further evaluate the role of disulfide bonds in the formation to octadecamer, we analyzed the role of reduction potential on adiponectin oligomerization. We observed that under immediate oxidizing conditions, hexamers and trimers form. Oxidized hexamer can form HMW adiponectin through disulfide bond rearrangement using beta-mercaptoethanol (βME) or increasing the total concentration of glutathione under oxidizing conditions. To further understand the role of disulfide bonds, we showed that zinc increased the oligomerization to octadecamer. This effect was associated with decreased initial disulfide bonding during the assembly to the octadecamer. In summary, these data suggest the rate of disulfide bond formation and the ability to undergo disulfide bond isomerization are important in the oligomerization process of HMW adiponectin.