title: Structure-based rational design of streptavidin mutants with pseudo-catalytic activity.
abstract: Introduction of enzymatic activity into proteins or other types of polymers by rational design is a major objective in the life sciences. To date, relatively low levels of enzymatic activity could be introduced into antibodies by using transition-state analogues of haptens. In the present study, we identify the structural elements that contribute to the observed hydrolytic activity in egg white avidin, which promote the cleavage of active biotin esters (notably biotinyl p-nitrophenyl ester). The latter elements were then incorporated into bacterial streptavidin via genetic engineering. The streptavidin molecule was thus converted from a protector to an enhancer of hydrolysis of biotin esters. The conversion was accomplished by the combined replacement of a "lid-like loop" (L3,4) and a leucine-to-arginine point mutation in streptavidin. Interestingly, neither of these elements play a direct role in the hydrolytic reaction. The latter features were thus shown to be responsible for enhanced substrate hydrolysis. This work indicates that structural and non-catalytic elements of a protein can be modified to promote the induced fit of a substrate for subsequent interaction with either a catalytic residue or water molecules. This approach complements the conventional design of active sites that involves direct modifications of catalytic residues.
authors.affiliation: Department of Biological Chemistry, The Institute of Life Sciences, The Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Pazy
authors.forename: Bilha
authors.initials: B
authors.lastname: Raboy
authors.forename: Meirav
authors.initials: M
authors.lastname: Matto
authors.forename: Edward A
authors.initials: EA
authors.lastname: Bayer
authors.forename: Meir
authors.initials: M
authors.lastname: Wilchek
authors.forename: Oded
authors.initials: O
authors.lastname: Livnah
mesh_terms: D001120:Arginine / Q000737:chemistry; D001360:Avidin / Q000737:chemistry; D001665:Binding Sites; D002384:Catalysis; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007930:Leucine / Q000737:chemistry; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017354:Point Mutation; D011108:Polymers / Q000737:chemistry; D011485:Protein Binding; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D019809:Streptavidin / Q000737:chemistry* / Q000235:genetics*; D013997:Time Factors
chemical_list: D011108:Polymers; D001360:Avidin; D019809:Streptavidin; D001120:Arginine; D007930:Leucine