Alpha-1-proteinase inhibitor is a heparin binding serpin: molecular interactions with the Lys rich cluster of helix-F domain.
Alpha-1-proteinase (alpha-1-PI) inhibitor is the major circulating serine protease inhibitor in humans. The porcine elastase and trypsin inhibitory activity of human and ovine alpha-1-PI is activated several fold in the presence of anti-coagulant heparin. The activation is allosteric and appears to be characterized by two steps of binding; a weak followed by a strong binding. The Kass for ovine and human alpha-1-PI inhibition of porcine pancreatic elastase was increased approximately 45 fold and 38 fold respectively. Using a combinatorial approach of multiple sequence alignment, surface topology, chemical modification and tryptic peptide mapping to identify the sequence of the heparin bound peptide; we demonstrate that heparin binds to the lysyl rich region of the F-helix of alpha-1-PI, which differs from that of heparin-antithrombin (AT) interactions. Molecular docking prediction using the MEDock algorithm approximates the three positively charged lysines (K154, K155, K174) of human alpha-1-PI in this interaction. This heparin alpha-1-PI interaction has been exploited to develop an affinity purification method, which can be used universally to obtain homogenous preparations of mammalian alpha-1-PIs useful for augmentation therapy. Collectively, all these findings imply that alpha-1-PI has a major role in regulating extra cellular protease activity and the physiological activator is heparin.
Gupta
Vivek Kumar
VK
Department of Protein Chemistry and Technology, Central Food Technological Research Institute, Mysore 570020, India.
Gowda
Lalitha R
LR
D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015843:Serpins / Q000737:chemistry* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000515:alpha 1-Antitrypsin / Q000737:chemistry* / Q000378:metabolism
D015843:Serpins; D000515:alpha 1-Antitrypsin; D006493:Heparin; D008239:Lysine