Cysteine residues 9-lactamase

The amino acid composition of the /3-lactamases listed in Table III (2, 40, 41, 43, 45, 54, 55, 58, 62-64) underlines the similarities between preparations derived from closely related strains of bacteria, especially if the combined basic and acidic amino acid content is compared (23). The staphylococcal enzymes are remarkably rich in lysine, and the lysine-arginine content of the other gram-positive /3-lactamases is almost as high. Complete absence of cysteine appears to be characteristic (2, 55), although j3-lactamases which contain at least one cysteine residue have been reported (37, 65, 66). 

Sigal, I.S. Harwood, B.G. Arentzen, R. Thiol-beta-lactamase—replacement of the active-site serine of RTEM beta-lactamase by a cysteine residue. Proc. Natl. Acad. Sci. USA. 1982, 79 (23), 7157-7160. 

A mutant of the non-electroactive enzyme 3-lactamase where residue TyrlOS located close the active site was replaced by a cysteine by site-directed mutagenesis was successfully labeled with 24 and the redox potential of the probe was seen to shift by 20 mV in the presence of a suicide substrate in the enzyme active site... 

---