@article{mbs:/content/journal/micro/10.1099/00221287-144-8-2025, author = "Winram, Scott B. and Lottenberg, Richard", title = "Site-directed mutagenesis of streptococcal plasmin receptor protein (Plr) identifies the C-terminal Lys334 as essential for plasmin binding, but mutation of the plr gene does not reduce plasmin binding to group A streptococci", journal= "Microbiology", year = "1998", volume = "144", number = "8", pages = "2025-2035", doi = "https://doi.org/10.1099/00221287-144-8-2025", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-144-8-2025", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "glyceraldehyde-3-phosphate dehydrogenase (GAPDH)", keywords = "plasmin(ogen)", keywords = "streptococci", keywords = "receptors", abstract = "Plasmin(ogen) binding is a common property of many pathogenic bacteria including group A streptococci. Previous analysis of a putative plasmin receptor protein, Plr, from the group A streptococcal strain 64/14 revealed that it is a glyceraldehyde-3-phosphate dehydrogenase and that the plr gene is present on the chromosome as a single copy. This study continues the functional characterization of Plr as a plasmin receptor. Attempts at insertional inactivation of the plr gene suggested that this single-copy gene may be essential for cell viability. Therefore, an alternative strategy was applied to manipulate this gene in vivo. Site-directed mutagenesis of Plr revealed that a C-terminal lysyl residue is required for wild-type levels of plasmin binding. Mutated Plr proteins expressed in Escherichia coli demonstrated reduced plasmin-binding activity yet retained glyceraldehyde-3-phosphate dehydrogenase activity. A novel integration vector was constructed to precisely replace the wild-type copy of the plr gene with these mutations. Isogenic streptococcal strains expressing altered Plr bound equivalent amounts of plasmin as wild-type streptococci. These data suggest that Plr does not function as a unique plasmin receptor, and underscore the need to identify other plasmin-binding structures on group A streptococci and to assess the importance of the plasminogen system in pathogenesis by inactivation of plasminogen activators and the use of appropriate animal models.", }