The active site of the aspartic proteinase, endothiapepsin, has been defined by X-ray analysis and restrained least-squares refinement at 2.1 A resolution with a crystallographic agreement value of 0.16. The environments of the two catalytically important aspartyl groups are remarkably similar and the contributions of the NH2- and COOH-terminal domains to the catalytic centre are related by a local 2-fold axis ...
The active site of the aspartic proteinase, endothiapepsin, has been defined by X-ray analysis and restrained least-squares refinement at 2.1 A resolution with a crystallographic agreement value of 0.16. The environments of the two catalytically important aspartyl groups are remarkably similar and the contributions of the NH2- and COOH-terminal domains to the catalytic centre are related by a local 2-fold axis. The carboxylates of the aspartyls share a hydrogen bond and have equivalent contacts to a bound water molecule or hydroxonium ion lying on the local diad. The main chains around 32 and 215 are connected by a novel interaction involving diad-related threonines. It is suggested that the two pKa values of the active site aspartyls arise from a structure not unlike that in maleic acid with a hydrogen-bonded intermediate species and a dicarboxylate characterised by electrostatic repulsions between the two negatively charged groups.
Related Citations:
Active Site of Acid Proteinases Blundell, T.L., Jones, H.B., Khan, G., Taylor, G., Sewell, T.S., Pearl, L.H., Wood, S.P. (1979) Proc Febs Meet 60: 281
The Three-Dimensional Structure of Acid Proteinases Blundell, T.L., Jenkins, J.A., Khan, G., Roychowdhury, P., Sewell, T., Tickle, I.J., Wood, E.A. (1979) Proc Febs Meet 52: 81
Four-Fold Structural Repeat in the Acid Proteases Blundell, T.L., Sewell, B.T., Mclachlan, A.D. (1979) Biochim Biophys Acta 580: 24
Structural Evidence for Gene Duplication in the Evolution of Acid Proteases Tang, J., James, M.N.G., Hsu, I.N., Jenkins, J.A., Blundell, T.L. (1978) Nature 271: 618
Homology Among Acid Proteases. Comparison of Crystal Structures at 3 Angstroms Resolution of Acid Proteases from Rhizopus Chinensis and Endothia Parasitica Subramanian, E., Swan, I.D.A., Liu, M., Davies, D.R., Jenkins, J.A., Tickle, I.J., Blundell, T.L. (1977) Proc Natl Acad Sci U S A 74: 556
X-Ray Analysis and Circular Dichroism of the Acid Protease from Endothia Parasitica and Chymosin Jenkins, J., Tickle, I., Sewell, T., Ungaretti, L., Wollmer, A., Blundell, T. (1977) Adv Exp Med Biol 95: 43
Organizational Affiliation:
Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India.
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