USE OF SINGLE-CYSTEINE MUTANTS TO PROBE THE LOCATION OF THE DISULFIDEBOND IN LAMB PROTEIN FROM ESCHERICHIA-COLI

The two cysteine residues of the LamB protein of Escherichia coli oute r membrane have been shown to form an intrasubunit disulfide whose loc ation differs greatly in the two current topology models of the LamB p rotein. This study probes the location of the disulfide by examining c onditions for intersubunit disulfide formation in single-cysteine muta nts of LamB protein. Formation of an intersubunit bond in the purified mutant proteins, which resulted in a disulfide-linked dimer, only occ urred after heat treatment, suggesting the disulfide is not exposed on the surface in the native protein. (C) 1994 Academic Press, Inc.