Structure of a mercaptan-thermolysin complex illustrates mode of inhibition of zinc proteases by substrate-analogue mercaptans

Biochemistry. 1982 Jul 6;21(14):3390-4. doi: 10.1021/bi00257a022.


The structure of the complex of thermolysin and the inhibitor (2-benzyl-3-mercaptopropanoyl)-L-alanylglycinamide has been determined by X-ray crystallography at a resolution of 1.9 A and refined to a crystallographic residual of 18.4%. The binding of this potent, specific inhibitor to thermolysin (Ki = 7.5 X 10(-7) M) serves as a model for the inhibition of zinc peptidases by substrate-analogue mercaptans. The study shows that the mercaptan inhibitor binds to thermolysin with the sulfur, presumably in the anionic form, tetrahedrally coordinated to the zinc and displacing a water molecule bound to the native enzyme. This is the first direct determination of the mode of binding of a mercaptan inhibitor to a zinc peptidase and confirms the geometry of binding expected on general grounds [Ondetti, M. A., Condon, M. E., Reid, J., Sabo, E. F., Cheung, H. S., & Cushman, D. W. (1979) Biochemistry 18, 1427-1430; Nishino, N., & Powers, J. C. (1979) Biochemistry 18, 4340-4347] and inferred from previous spectroscopic studies [Holmquist, B., & Vallee, B. L. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 6216-6220].

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3-Mercaptopropionic Acid / analogs & derivatives
  • 3-Mercaptopropionic Acid / pharmacology
  • Binding Sites
  • Kinetics
  • Metalloendopeptidases
  • Models, Molecular
  • Protease Inhibitors* / metabolism*
  • Sulfhydryl Compounds / metabolism*
  • Thermolysin / metabolism*
  • Zinc / metabolism


  • Protease Inhibitors
  • Sulfhydryl Compounds
  • 2-benzyl-3-mercaptopropanoyl-alanylglycinamide
  • 3-Mercaptopropionic Acid
  • Metalloendopeptidases
  • Thermolysin
  • Zinc