tailieunhanh - Báo cáo Y học: Disul®de bond formation through Cys186 facilitates functionally relevant dimerization of trimeric hyaluronan-binding protein 1 (HABP1)/p32/gC1qR

Hyaluronan-binding protein 1 (HABP1), a ubiquitous multifunctional protein, interacts with hyaluronan, globular head of complement component 1q (gC1q), and clustered mannose and has been shown to be involved in cell vitro, this recombinant protein isolated from human ®broblast exists in di erent oligomeric forms, as is evident from the results of various independent techniques in near-physiological conditions. | Eur. J. Biochem. 269 298-306 2002 FEBS 2002 Disulfide bond formation through Cys186 facilitates functionally relevant dimerization of trimeric hyaluronan-binding protein 1 HABP1 p32 gC1qR Babal Kant Jha1 Dinakar M. Salunke2 and Kasturi Datta1 1 Biochemistry Laboratory School of Environmental Sciences Jawaharlal Nehru University New Delhi India 2Structural Biology Unit National Institute of Immunology Aruna Asaf Ali Marg New Delhi India Hyaluronan-binding protein 1 HABP1 a ubiquitous multifunctional protein interacts with hyaluronan globular head of complement component 1q gC1q and clustered mannose and has been shown to be involved in cell signalling. In vitro this recombinant protein isolated from human fibroblast exists in different oligomeric forms as is evident from the results of various independent techniques in near-physiological conditions. As shown by size-exclusion chromatography under various conditions and glutaraldehyde cross-linking HABP1 exists as a noncovalently associated trimer in equilibrium with a small fraction of a covalently linked dimer of trimers . a hexamer. The formation of a covalently-linked hexamer of HABP1 through Cys186 as a dimer of trimers is achieved by thiol group oxidation which can be blocked by modification of Cys186. The gradual structural transition caused by cyste-ine-mediated disulfide linkage is evident as the fluorescence intensity increases with increasing Hg2 concentration until all the HABP1 trimer is converted into hexamer. In order to understand the functional implication of these transitions we examined the affinity of the hexamer for different ligands. The hexamer shows enhanced affinity for hyaluronan gC1q and mannosylated BSA compared with the trimeric form. Our data analyzed with reference to the HABP1 p32 crystal structure suggest that the oligomerization state and the compactness of its structure are factors that regulate its function. Keywords clustered mannose hyaluronan hyaluronan-binding protein 1 .