Role of surface protein SasG in biofilm formation by Staphylococcus aureus.
The SasG surface protein of Staphylococcus aureus has been shown to promote the formation of biofilm. SasG comprises an N-terminal A domain and repeated B domains. Here we demonstrate that SasG is involved in the accumulation phase of biofilm, a process that requires a physiological concentration of Zn(2+). The B domains, but not the A domain, are required. Purified recombinant B domain protein can form dimers in vitro in a Zn(2+)-dependent fashion. Furthermore, the protein can bind to cells that have B domains anchored to their surface and block biofilm formation. The full-length SasG protein exposed on the cell surface is processed within the B domains to a limited degree, resulting in cleaved proteins of various lengths being released into the supernatant. Some of the released molecules associate with the surface-exposed B domains that remain attached to the cell. Studies using inhibitors and mutants failed to identify any protease that could cause the observed cleavage within the B domains. Extensively purified recombinant B domain protein is very labile, and we propose that cleavage occurs spontaneously at labile peptide bonds and that this is necessary for biofilm formation.
Geoghegan
Joan A
JA
Microbiology Department, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
Corrigan
Rebecca M
RM
Gruszka
Dominika T
DT
Speziale
Pietro
P
O'Gara
James P
JP
Potts
Jennifer R
JR
Foster
Timothy J
TJ
D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D002473:Cell Wall; D002614:Chelating Agents / Q000494:pharmacology; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D013294:Lactococcus lactis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D004369:Pentetic Acid / Q000494:pharmacology; D010957:Plasmids; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D013211:Staphylococcus aureus / Q000235:genetics / Q000502:physiology*; D013212:Staphylococcus epidermidis; D015032:Zinc / Q000378:metabolism
D001426:Bacterial Proteins; D002614:Chelating Agents; D008565:Membrane Proteins; D011994:Recombinant Proteins; C524374:SasG protein, Staphylococcus aureus; D004369:Pentetic Acid; D015032:Zinc
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