Complement factor D is a serine protease regulated by a novel mechanism that depends on conformational changes rather than cleavage of a zymogen for expression of proteolytic activity. The conformational changes are presumed to be induced by the single n ...
Complement factor D is a serine protease regulated by a novel mechanism that depends on conformational changes rather than cleavage of a zymogen for expression of proteolytic activity. The conformational changes are presumed to be induced by the single natural substrate, C3bB, and to result in reversible reorientation of the catalytic center and of the substrate binding site of factor D, both of which have atypical conformations. Here we report that replacement of Ser94, Thr214, and Ser215 of factor D (chymotrypsinogen numbering has been used for comparison purposes) with the corresponding residues of trypsin, Tyr, Ser, and Trp, is sufficient to induce substantially higher catalytic activity associated with a typical serine protease alignment of the catalytic triad residues His57, Asp102, and Ser195. These results provide a partial structural explanation for the low reactivity of "resting-state" factor D toward synthetic substrates.
Related Citations:
Catalytic Role of a Surface Loop of the Complement Serine Protease Factor D Kim, S., Narayana, S.V., Volanakis, J.E. (1995) J Immunol 154: 6073
Mutational Analysis of the Substrate Binding Site of Human Complement Factor D Kim, S., Narayana, S.V., Volanakis, J.E. (1994) Biochemistry 33: 14393
Structure of Human Factor D. A Complement System Protein at 2.0 A Resolution Narayana, S.V., Carson, M., El-Kabbani, O., Kilpatrick, J.M., Moore, D., Chen, X., Bugg, C.E., Volanakis, J.E., Delucas, L.J. (1994) J Mol Biol 235: 695
Crystallization and Preliminary X-Ray Investigation of Factor D of Human Complement Narayana, S.V., Kilpatrick, J.M., El-Kabbani, O., Babu, Y.S., Bugg, C.E., Volanakis, J.E., Delucas, L.J. (1991) J Mol Biol 219: 1
Organizational Affiliation:
Department of Medicine, University of Alabama at Birmingham 35294-0006, USA.
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