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BIOLOGICAL SCIENCES / BIOCHEMISTRY
Differential P1 arginine and lysine recognition in the prototypical proprotein convertase Kex2
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160
Communicated by Gregory A. Petsko, Brandeis University, Waltham, MA, March 7, 2007 (received for review October 4, 2006)
The high-resolution crystal structure of kexin (Kex2) in complex with a peptidyl-chloromethylketone inhibitor containing a noncognate lysine at the P1 position provides the structural basis for the differential lysine/arginine selectivity that defines the prohormone (proprotein) convertase (PC) family. By comparison with the previous structures of Kex2 and furin, this structure of the acylated enzyme provides a basis for the observed decrease in the acylation rate with substrates containing a lysine at P1 and the absence of an effect on the deacylation rate without involving mobility of the S1 lid. The structure of the complex shows that a secondary subsite in the S1 pocket is present, and that this site recognizes and binds the P1 lysine in a more shallow fashion than arginine. This results in a displacement of the bound peptide away from the S385 nucleophile relative to substrates containing a P1 arginine. It is concluded that this alternate binding site and resultant displacement of the scissile bond in the active site results in the observed decrease in the acylation rate. Studies of the inactivation kinetics of Kex2 by two peptidyl chloromethylketone inhibitors demonstrates that the selectivity between lysine and arginine at the P1 position arises at the acylation step, consistent with what was observed with peptidyl substrates [Rockwell NC, Fuller RS (2001) J Biol Chem 276:38394–38399].
chloromethylketone | crystallography | furin
The authors declare no conflict of interest.
Data deposition: The atomic coordinates reported in this paper have been deposited in the Protein Data Bank, www.pdb.org (PDB ID code 2ID4).
The designation of the substrate residues follows the naming convention of Schechter and Berger (45). Briefly, starting at the scissile bond and counting toward the N terminus, the substrate residues are designated P1, P2, P3.... Conversely, the substrate residues are bound at the corresponding S1, S2, or S3 subsite on the enzyme.
This article contains supporting information online at www.pnas.org/cgi/content/full/0701983104/DC1.
*To whom correspondence should be addressed. E-mail: tholyoak{at}kumc.edu
© 2007 by The National Academy of Sciences of the USA
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