From structural analysis on genetically abnormal and chemically modified human antithrombin Ill [Koide, T., Odani, S., Takahashi, K., Ono, T. and Sakuragawa, N. (1984) Proc. Natl Acad. Sci. USA 81,[289][290][291][292][293] Chang, J.-Y. and Tran, T. H., (1986) J. Biol. Chem. 261, 1174-1176Blackburn, M. N., Smith, R. L., Carson, J. and Sibley, C. C. (1984) J . Biol. Chem. 259,, the heparin-binding site of antithrombin 111 has been suggested to be in the region of Pro-41, Arg-47 and Trp-49. In this study the heparin-binding site was probed by preferential cleavage of V8 protease on heparin-treated and non-treated native antithrombin 111. The study has been based on the presumption that the heparin-binding site of antithrombin 111 is situated at exposed surface domain and may be preferentially attacked during limited proteolytic digestion. Partially digested antithrombin I11 samples were monitored by quantitative amino-terminal analysis and amino acid sequencing to identify the preferential cleavage sites. 1-h-digested antithrombin 111 was separated on HPLC and peptide fragments were isolated and characterized both qualitatively and quantitatively. The results reveal that Glu-Gly (residues 34 -39, Glu-Ala (residues 42-43) and Glu-Leu (residues 50-51) are three preferential cleavage sites for V8 protease and their cleavage, especially the Glu-Ala and the Glu-Leu sites, was drastically inhibited when antithrombin 111 was preincubated with heparin. Both high-affinity and low-affinity antithrombin-111-binding heparins were shown to inhibit the V8 protease digestion of native antithrombin 111, but the high-affinity sample exhibited a higher inhibition activity than the low-affinity heparin. These findings (a) imply that the segment containing residues 34-51 is among the most exposed region of native antithrombin I11 and (b) support the previous conclusions that this region may play a pivotal role in the heparin binding.The plasma glycoprotein, antithrombin 111, regulates the blood-blotting system by inhibiting a number of hemostatic proteases, such as thrombin and factors IXa, Xa, XIa and XIIa. These reactions are greatly accelerated by the polysaccharide heparin [l -31. Elucidation of the molecular basis for the inhibitory action of antithrombin I11 in the presence of heparin has been complicated by the fact that heparin binds not only to antithrombin 111 but also with the cognate enzymes like thrombin and factor IXa [l, 41. Different models have been proposed to account for the mechanism of heparin function [5 -141. One model that has been studied in detail showed that heparin combines with antithrombin 111 to induce conformational change for more competent inhibitory function [15 -201. The heparin -antithrombin-111 complex is apparently formed by the electrostatic interaction between the acidic groups (mostly sulfate) of heparin [9, 211 and the Lys/ Arg residues of antithrombin 111 122 -281 the region including Pro-41, Arg-47 and Trp-49 could be the potential heparin-binding site of antithrombin 111.In this paper ...

The amino acid sequences of pike eel gonadotropin a and p subunits have been determined by standard sequencing analytical methods. The a subunit is composed of 93 amino acid residues while the j subunit comprises 113 amino acid residues. All the invariant half-cystine residues are in the same positions as those found in other gonadotropins.It is noteworthy that the first, putative glycosylation site (Asn56) found in the a subunit of other gonadotropins was replaced by Asp56 in the a subunit of pike eel gonadotropin. Similarity analyses indicate that both subunits are structurally more similar to other known fish gonadotropin subunits than to those of the mammalian gonadotropins.Gonadotropin belongs to a family of glycoprotein hormones which are secreted from the anterior pituitary and placenta. It is composed of two subunits, a highly conserved u subunit and an activity-dictating fl subunit, while hormonal activity occus only after noncovalent interaction between an cc subunit and a /I subunit [I, 21. From previous cumulative studies on the pituitary gonadotropins of the mammals, birds, reptiles (except snakes) and amphibians [3], it becomes clear that two types of gonadotropins exist, namely follitropin and lutropin. As the names imply, they stimulate testicular and ovarian functions by means of regulation of gametogenesis and steroid hormone synthesis [4]

Two analogous protease inhibitors, VIIIb and IX in the venom of Bungarus fasciatus were reduced and carboxymethylated. Tryptic peptides were separated by cellulose thin‐layer peptide mapping technique, and amino acid sequences were analyzed by DABITC/PITC double coupling method. Alignment of all tryptic peptides was established by analyses of chymotryptic peptides and further confirmed by Staphylococcus aureus V8 protease digestion. IX consisted of 65 amino acid residues. VIIIb consisted of 62 residues, identical to the N‐terminal 62‐amino acid sequence of IX.

Hemoglobin G Taegu, an electrophoretically slow hemoglobin variant found in four among 6700 apparently normal Korean subjects, has been shown to have a structural anomaly at position 22 of the beta‐chain where an alanyl residue occurs in place of the glutamyl group normally found at that position in Hemoglobin A.The same structural anomaly initially was established by other workers in slow hemoglobin variants occurring in North American Indians and more recently has been reported in a Northern Chinese subject. The identical hemoglobins in the three ethnic groups are Hemoglobins G Coushatta, found in several Alabama‐Coushatta Indians in Tex.; G Saskatoon, seen in a few descendants of Santee Indians currently living in Canada; G Hsin‐Chu, in a Chinese from the northern province of Liaoning and currently living in Taiwan; and G Taegu in Koreans.It is assumed that the Chinese and Korean subjects have the same hemoglobin variant because of gene flow. No similar assumption connecting these two groups with the North American Indian subjects is considered warranted with the presently limited available information.