Dear Crystallographers, I am working with a cysteine protease. I co-crystallized the protease with some small chemically synthesised peptides of 7 amino acid residues. I mutated the active Cysteine residue with Alanine to avoid the peptide cleavage so that I can get the whole peptide bound with my protein. But interesting I got the density for a cleaved peptide with 4 amino acids instead of the whole peptide. The resolution is 1.4 A, I can see the clear cleavage and the cleavage occurred exactly at the same peptide bond where it should. But I do not know how!
Now my question is why I am getting the cleaved peptide as I already mutated the active residue Cysteine with Alanine (this mutant did no show any activity when I checked with SDS-PAGE). If anybody has the same kind of experience please advice me. Thanks in advance. Best, Dipankar -- Dipankar Manna Research Scholar Department of Chemistry University of Oslo Oslo, Norway
