CHARACTERIZATION OF LPXTGASE FROMSTAPHYLOCOCCUS AUREUS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bacterial surface proteins are important molecules in the infectivity and survival of pathogens. Surface proteins on gram-positive bacteria have been shown to attach via a transpeptidase, termed sortase, that cleaves an LPXTG sequence found close to the C termini of nearly all surface proteins on these bacteria. We previously identified a unique enzyme (LPXTGase) from Streptococcus pyogenes that also cleaves the LPXTG motif with a catalytic activity higher than that of sortase, suggesting that it plays an important role in the attachment process. We have now purified and characterized an LPXTGase from Staphylococcus aureus and found that it has both similar and unique features compared to the S. pyogenes enzyme. The S. aureus enzyme is glycosylated and contains unusual amino acids, like its streptococcal counterpart. Like the streptococcal enzyme, staphylococcal LPXTGase has an overrepresentation of amino acids found in the peptidoglycan, i.e., glutamine/glutamic acid, glycine, alanine, and lysine, and furthermore, we find that these amino acids are present in the enzyme at precisely the same ratio at which they are found in the peptidoglycan for the respective organism. This suggests that enzymes responsible for wall assembly may also play a role in the construction of LPXTGase. In the present work, we are seeking to sequence these unusual enzymes by mass spectrometry.