Only a few conserved residues are located within this predicted peptide loop connecting the Walker A and B motifs. A detailed mutational analysis of the HisP protein from
S.typhimurium revealed that in most cases amino acid substitutions, while a¡ecting
transport, did not alter nucleotide binding activity. In line with these ¢ndings was the observation that mutation of a highly conserved glutamine residue in MalK (Q82) did not signi¢cantly reduce the ATPase activity of the puri¢ed protein.