| Popis: |
Antistasin is a 119 amino acid protein with anticoagulant, antimetastatic and heparin-binding properties derived from the salivary glands of the leech Haementaria officinalis (1). This protein contains a specific consensus sequence for heparin binding at its carboxyl terminal end and a region between residues 32 and 48 putatively involved in glycosaminoglycan interactions. The cyclic peptide antistasin 37-48 (C-P-H-G-F-Q-R-S-R-Y-G-C) and the carboxyl terminal fragment [A103,106,108] antistasin 93-119 (P-N-G-L-K-R-D-K-L-G-A-E-Y-A-E-A-R-P-K-R-K-L-I-P-R-L-S) were synthesized by solid-phase peptide chemistry and their interactions with 125I-labeled heparin were investigated. Heparin binding to [A103,106,108] antistasin 93-119 was specific and saturable as binding was blocked by addition of the unlabeled glycosaminoglycan. The rank order of potency of various glycosaminoglycans in blocking 125I-labeled heparin binding to [A103,106,108] antistasin 93-119 was dextran sulfate greater than heparin much greater than dermatan sulfate greater than or equal to chondroitin sulfate A and C indicating a specificity of the peptide for the glycosaminoglycan structure. Moreover, heparin binding increased linearly with increasing salt and was optimal at 0.15 M NaCl and physiological pH. In contrast, binding of heparin to the basic peptide antistasin 37-48 decreased linearly as the ionic strength of the medium was increased to physiological concentration (0.15 M) thus showing a greater specificity of heparin for [A103,106,108] antistasin 93-119. These studies indicate that residues 93-119 of antistasin mediate this inhibitor's interaction with heparin. |
