ISOLATION, CLONING, AND EXPRESSION OF A 70-KILODALTON PLASMINOGEN BINDING-PROTEIN OF BORRELIA-BURGDORFERI

Surface receptors for plasminogen are expressed by many gram-positive and gram-negative bacteria and may play a role in the dissemination of organisms by binding plasminogen, which upon conversion to plasmin ca n digest extracellular matrix proteins, Two plasminogen binding protei ns have been identified for Borrelia burgdorferi, outer surface protei n A and a 70-kDa protein (BPBP), We purified BPBP by plasminogen affin ity chromatography and obtained its amino acid sequence by Edman degra dation of a tryptic digest, The gene coding for BPBP was isolated from a h-ZAP II genomic library with probes developed from sequenced porti ons of the protein, This gene was expressed in Escherichia coli; the r ecombinant product was seen by antibody raised against native BPBP and also bound I-125-labeled plasminogen. The experimentally derived amin o acid sequences corresponded to the predicted sequence encoded by the BPBP gene, The deduced amino acid sequence for BPBP revealed signific ant similarity to p30, a 30-kDa protein of B. burgdorferi (54% identit y and 65% similarity), to a 60-kDa protein in Borrelia coriaceae (66% identity and 80% similarity), to oligopeptide binding protein A of E. coli (34% identity and 57% similarity), and, more generally, to the pe riplasmic oligopeptide binding family of proteins.