Identification of critical residues of the serotype modifying O-acetyltransferase of Shigella flexneri

BMC Biochemistry

Table 1 Amino acid residues in Oac targeted for mutagenesis

Mutation	Location of mutation in Oac	Basis of selection for mutagenesis
SG 52-53	TM II	Part of conserved motif FFiSG
R 62	Loop 3	Positively charged amino acid in cytoplasmic loop. Shows some level of conservation with homologous acetyltransferases.
R 73	Loop 3	Positively charged amino acid in cytoplasmic loop. Shows some level of conservation with homologous acetyltransferases.
RR 75-76	Loop 3	Positively charged amino acid R75 shows some level of conservation. R76 is highly conserved and belongs to motif RIfPAL.
FP 78-79	TM III	Part of conserved motif RIfPAL.
C 84	TM III	To investigate if it forms disulphide bonds with other cysteine residues in Oac.
RK 110-111	Loop 4	Positively charged amino acid in periplasmic loop. Not conserved in location; thus mutated to determine if amino acid charge was important to position.
S 114	Loop 4	Neutral amino acid in periplasmic loop. Not conserved in location; thus mutated to determine if amino acid charge was important to position.
GS 138-139	TM IV	Part of conserved motif NGsLWT
WT 141-142	TM IV	Part of conserved motif NGsLWT
GR 269-270	Loop 9	Shows some level of conservation with homologous acetyltransferases. Present in a cytoplasmic loop
SYG 274-276	TM IX	Part of conserved motif SYGxY
FPV 282-284	TM IX	Part of conserved motif FPVQQ
D 333	Loop 11	Negatively charged amino acid in cytoplasmic loop. Not conserved in location; thus mutated to determine if amino acid charge was important to position.

The location of residues targeted for mutagenesis and the rationale for their selection have been described. The red colour indicates residues chosen for mutagenesis. Lower case characters in motifs represent residues which are found only in Oac and are not conserved.

ISSN: 1471-2091