Structural consideration of the formation of the activation complex between the staphylokinase-like streptococcal plasminogen activator PadA and bovine plasminogen |
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Authors: | Ward Philip N Abu-Median Abu-Bakr A K Leigh James A |
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Affiliation: | 1 Nuffield Department of Clinical Laboratory Sciences, Oxford University, John Radcliffe Hospital, Headington OX3 9DU, UK 2 Institute for Animal Health, Compton Laboratory, Compton, Berkshire RG20 7NN, UK 3 School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD, UK |
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Abstract: | The characteristics of a streptococcal plasminogen activator (PA) displaying specificity for ruminant plasminogen (Plg) were defined using molecular approaches. The 16-kDa secreted protein PadA was found to be prevalent in Streptococcus dysgalactiae subspecies dysgalactiae isolated from cases of bovine mastitis and septic arthritis in lambs. PadA was able to activate bovine, ovine and caprine Plg, but not human Plg. Amino acid sequence analysis identified a limited level of homology to other streptococcal PAs, including streptokinase; however, PadA was found to align well with and match in size the staphylococcal PA, staphylokinase. Recombinant PadA was used to investigate interaction with bovine Plg, leading to formation of an activator complex that was capable of recruiting and converting further substrate Plg into plasmin. Individual non-overlapping peptides of PadA or bovine microplasminogen were found to block the interaction between PadA and bovine Plg, preventing the formation of the activation complex. Homology modelling based upon structures of staphylokinase complexed with human microplasminogen supported these findings by placing critical residues in close proximity to the plasmin component of the activation complex. |
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Keywords: | PA, plasminogen activator Plg, plasminogen Plm, plasmin SK, streptokinase SAK, staphylokinase μPlm, microplasmin μPlg, microplasminogen hPlg, human plasminogen bPlg, bovine plasminogen ORF, open reading frame rPadA, recombinant PadA NPGB, p-nitrophenyl-p-guanidinobenzoate hμPlm, human microplasmin PDB, Protein Data Bank bμPlm, bovine microplasmin bμPlg, bovine microplasminogen hμPlg, human microplasminogen PBS, phosphate-buffered saline |
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