The ESAT-6/WXG100 superfamily -- and a new Gram-positive secretion system?
ESAT-6 is a small secreted protein of unknown function from Mycobacterium tuberculosis that is of fundamental importance in virulence and protective immunity. A PSI-BLAST search has identified distant homologues of ESAT-6 in more tractable bacteria, including Bacillus subtilis, Bacillus anthracis, Staphylococcus aureus and Clostridium acetobutylicum. The genes for ESAT-6-like proteins often cluster with genes encoding homologues of B. subtilis YukA. I speculate that the ESAT-6-like and YukA-like proteins form a novel Gram-positive secretion system potentially driven by the FtsK/SpoIIIE ATPase domains in the YukA-like proteins. The way is now open to investigate this hypothesis in organisms that are easier to manipulate than pathogenic mycobacteria.
Pallen
Mark J
MJ
Division of Immunity and Infection, Birmingham University Medical School, Birmingham, UK B15 2TT. m.pallen@bham.ac.uk
D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology / Q000502:physiology*; D016824:Antigens, Human Platelet / Q000502:physiology; D001426:Bacterial Proteins; D001483:Base Sequence; D006094:Gram-Positive Bacteria / Q000235:genetics / Q000378:metabolism*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D009169:Mycobacterium tuberculosis / Q000235:genetics; D021381:Protein Transport; D016415:Sequence Alignment
C510800:4b alloantigen, human; D000942:Antigens, Bacterial; D016824:Antigens, Human Platelet; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis