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Gonococcal penicillin-binding protein 3 and the surface-exposed 44kDa peptidoglycan-binding protein appear to be the same molecule


  • W. M. Shafer,

    Corresponding author
    1. Laboratories of Microbial Pathogenesis, Medical Research Service, Veterans Affairs Medical Center, Decatur, Georgia 30033, USA.
    2. Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
    • *For correspondence. Tel. (404) 321 6111. ext. 7137: Fax (404) 728 7755.

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  • R. C. Judd

    1. Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA.
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The outer membrane of Neisseria gonorrhoeae contains a 44000 datton (44kDa) surface-exposed protein which has the reported ability to form covalent interactions with peptidoglycan (PG). This PG-binding outer-membrane protein (OMP) appears to be highly conserved since it has been detected in all isolates examined. It also appears to be invariant since its primary structure among strains gives evidence of being identical (Judd et al., 1991). While studying the interaction of gonococcal penicillin-binding proteins (PBPs) with human lysosomal cathepsin G, we noticed that the 44kDa PG-binding OMP exhibited certain properties similar to PBP3. In this study we sought to obtain biochemical evidence to ascertain whether these proteins were the same. We found that both proteins fractionated with other sarkosyl-insoluble OMPs and that they exhibited similar susceptibility to cleavage in situ by enzymatically active cathepsin G. Moreover, a purified preparation of the 44kDa OMP was found to covalently bind radiolabelled benzylpenicillin in vitro. Thus, the data presented herein suggest that the 44kDa PG-binding OMP and PBP3 are the same OMP.

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