Am. Stranden et al., CELL-WALL MONOGLYCINE CROSS-BRIDGES AND METHICILLIN HYPERSUSCEPTIBILITY IN A FEMAB NULL MUTANT OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS, Journal of bacteriology, 179(1), 1997, pp. 9-16
The femAB operon is involved in the formation of the characteristic pe
ntaglycine side chain of the staphylococcal peptidoglycan. Allele repl
acement of the femAB operon with the tetracycline resistance determina
nt tetK in a methicillin-resistant Staphylococcus aureus strain result
ed in impaired growth, methicillin hypersusceptibility, and lysostaphi
n resistance, The usual pentaglycine cross-bridges were replaced by mo
noglycine bridges exclusively, and cross-linking of the peptidoglycan
strands was drastically reduced. Complementation of the femAB null mut
ant by either femA or femAB resulted in the extension of the cross-bri
dges to a triglycine or a pentaglycine, respectively. This finding sug
gests that FemA is responsible for the formation of glycines 2 and 3,
and FemB is responsible for formation of glycines 4 and 5, of the pent
aglycine side chain of the peptido-glycan precursor. Moreover, it can
be deduced that addition of the first glycine must occur by a femAB-in
dependent mechanism.