Translation of the staphylokinase gene yields a protein with 163 amino acids, the first 27 of which represent a signal peptide. The processed mature protein has 136 amino acids, a molecular mass of 16.5 kDa, and is devoid of disulfide bridges. The N-terminal amino acid sequence of the mature protein is Lys-Gly-Asp-Asp-Ala . The three-dimensional structure of staphylokinase has also been elucidated (Figure 13.2). The protein has an elongated conformation with two folded domains of similar size, resulting in the flexible dumbbelllike shape. The protein consists of 9% a-helix and 22 to 39% P-sheet with a central 13-residue a-helix flanked by a two-stranded P-sheet, both of which are located above a five-stranded P-sheet [61-63].
Staphylokinase is a profibrinolytic agent. It is devoid of catalytic activity, but like strep-tokinase, it forms a 1:1 stoichiometric complex with plasmin and this complex activates
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