Human thrombin: Partial primary structure |
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Authors: | Arthur R Thompson David L Enfield Lowell H Ericsson Mark E Legaz John W Fenton |
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Institution: | 1. Departments of Medicine (Hematology) and Biochemistry, University of Washington, and the Puget Sound Blood Center, Seattle, Washington, U.S.A.;2. Division of Laboratories and Research, New York State Department of Health, Albany, New York, U.S.A. |
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Abstract: | Human thrombin, prepared from an extrinsically activated prothrombin, was finally chromatographed on an affinity column of p-chlorobenzylamido-?-aminocaproyl agarose. After reduction and s-pyridylethylation, the A and B chains were separated. The A chain contains 36 residues and no carbohydrate and has a formula weight of 4093. Its sequence corresponds to 14–49 of the bovine A chain sequence with nine replacements. Human B chain contains 264 residues. The carbohydrate content is 3.5% neutral sugar, 2.6% glucosamine, and 1.5% sialic acid. High-speed sedimentation equilibrium in guanidine gave a minimum molecular weight of 33,500. Sequenator analysis yielded the first 50 amino-terminal residues and established the positions of three of the cyanogen bromide fragments. A fourth fragment lacked homoserine and was placed at the carboxyl-terminus. The four remaining fragments, comprising half of the B chain, were tentatively assigned positions by assuming homology with bovine thrombin and with pancreatic serine proteases. Within the B chain, the active site histidine and serine were both in highly conservative regions, and an Arg-Tyr bond has been identified as a biological degradation site. Sixty-nine percent of the primary structure of human thrombin was identified by sequenator analysis. In comparing this sequence with that reported for the bovine molecule, 26 replacements are present. |
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Keywords: | Author to whom reprint requests should be addressed at Department of Hematology U S Public Health Service Hospital Seattle Washington 98114 |
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