The tryptic peptide containing the active-site cysteine in glyceraldehyde-3-phosphate dehydrogenase from Bacillus stearothermophilus 1503 was isolated after inhibition of the enzyme with (14)C-iodoacetate. The amino acid sequence of the 20-residue peptide was determined by 19 successive cycles of dansyl-Edman degradation. The sequence shows considerable homology with its counterparts from mesophilic sources but differs by the addition of Ala-His-His at the N-terminus and by the substitution of phenylalanine for leucine in the prototype sequence.
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge, England, Departments of Microbiology and Biochemistry, and the McIlvain Laboratories, University of Kansas Medical Center, Kansas City, Kansas 66103.
