Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An immunopeptide bearing a3 allotypic determinant(s) was isolated from the gamma chain of an a3 homozygous rabbit (G222-2) immunized with type III pneumococcal vaccine. Immunocogical properties of peptides were studied using a radioimmunoassay that involved inhibition by these peptides of a reaction between 125I-labeled anti-a3 antibody and Sepharose-bound a3 immunoglobulin G (IgG). The gamma chain was isolated from IgG of restricted heterogeneity and then citraconylated and digested with trypsin. The tryptic digest (TD1) was passed through an anti-a3 immunoabsorbent column either directly or after an intermediate step of Sephadex G-75 chromatography. The bound peptides (T1) were eluted with 0.1 M acetic acid and further digested with trypsin. The digest (TD2) was again run on the anti-a3 immunoabsorbent column to purify the bound immunopeptide T2. In the radioimmunossay this immunopeptide was found to have major a3 determinant(s). Its molecular weight was found to be approximately 6,000, which decreased to about 3,000 after reduction and alkylation. These data, together with NH2- and COOH-terminal analyses and cysteine peptide mapping, demonstrated that T2 is composed of two polypeptide chains linked by a disulfide bond, one from the cysteine 22 region having lysine at the COOH terminus and the other from the cysteine 92 region arginine at the COOH terminus. The lysine peptide was separated from the arginine peptide and its NH2-terminal sequence was found to be Gly-Asx-Glx-Ser-Thr-Cys. Since the cysteine is at position 22, the lysine peptide starts at position 17. It has approximately 22 residues. The framework sequence from 17 to 20 is different from those reported so far. In addition, the heavy chain used in these studies has some other unusual features including a histidine, probably in the first hypervariable region. The presence of histidine in the first hypervariable region of rabbit heavy chain has not been reported previously. The other peptide which is about 30 amino acids in length and ends with arginine 94, probably includes positions 67, 70, 71, 84, and 85 that are believed to have substitutions correlating with a allotypes. In a hypothetical three-deminsional model of the Fv portion of rabbit anti-SIII antibody BS-5, residues 17 to 33 of the lysine peptide and 67 to 79 and 84 to 85 which may be present in the arginine peptide are fully exposed on the surface and are far removed from the antibody combining site.
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PMID:Studies on the structural localization of rabbit H chain allotypic determinants controlled by the a locus. Purification and immunological properties of an immunopeptide bearing a3 allotypic determinants. 6 65

The effects of trypsin digestion and low temperature on Ca2+ binding and on Ca2+ activation of ATP hydrolysis by the high-affinity transport sites of the Ca2+, Mg2+-ATPase of sarcoplasmic reticulum were examined. Sarcoplasmic reticulum vesicles contain 0.7-1.1 high-affinity Ca2+ sites per 10(5) g sarcoplasmic reticulum with K = 3-5 X 10(5) M-1, as well as sites of lower affinity. The first cleavage of the ATPase with trypsin (TD1) has no effect on the binding properties of the high affinity sites. The second tryptic cleavage (TD2) decreases the affinity of the high sites to K = 3 X 10(4) M-1 with conservation of the total number of sites. The purified ATPase contains 1.6-2.0 high affinity Ca2+ sites per 10(5) g protein when measured at 23 degrees C, while at 0-4 degrees C there is approximately equal to 1 high-affinity (K = 5 - 10 X 10(5) M-1) affinity site and approximately equal to 1 intermediate-affinity (K = 3 X 10(4) M-1) site per 10(5) g. Trypsin digestion to the point of TD1 has no effect on either the number or the binding constants of the high-affinity sites. Upon TD2 cleavage, one of the sites is converted to the intermediate-affinity state, while the other remains at high affinity. After TD2 modification of the enzyme both of the sites are in the intermediate affinity state at 4 degrees C. On the basis of the binding data, several models for the roles of the Ca2+ sites in the activation of ATP hydrolysis are derived. The results are summarized by a scheme in which the two high-affinity Ca2+ sites are heterogeneous with respect to sensitivity to temperature and to TD2 modification. The results of this and a previous study [Scott, T. L. and Shamoo, A. E. (1982) J. Membr. Biol. 64, 137-144] indicate that while occupation of either of the two Ca2+ sites can stimulate ATP hydrolysis, the site which is sensitive to TD2 is essential for the coupling of hydrolysis to Ca2+ transport.
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PMID:Distinction of the roles of the two high-affinity calcium sites in the functional activities of the Ca2+-ATPase of sarcoplasmic reticulum. 623 83

The uncoupling of Ca2+ transport from ATP hydrolysis in the sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase by trypsin digestion was re-investigated by comparing ATPase activity with the ability of the enzyme to occlude Eu3+ (a transport parameter) after various tryptic digests. With this method, re-examination of uncoupling by tryptic digest of the ATPase revealed that TD2 cleavage (Arg-198) had no effect on either occlusion or ATPase activity. Digestion past TD2 in the presence of 5 mM Ca2+ and at 25 degrees C resulted in the loss of about 70% of the ATPase activity, but no loss of occlusion. Digestion past TD2 in the presence of 5 mM Ca2+, 3 mM ATP, and at 25 degrees C resulted in a partially uncoupled enzyme complex which retained about 50% of the ATPase activity, but completely lost the ability to occlude Eu3+. Digest past TD2 in the presence of 5 mM Ca2+ and 3 mM AMP-PNP (a non-hydrolyzable ATP analog) at 25 degrees C resulted in no loss of occlusion, thus revealing the absolute requirement of ATP during the digest to eliminate occlusion. From these findings we conclude that uncoupling of Ca2+ transport from ATPase activity is possible by tryptic digestion of the (Ca2+ + Mg2+)-ATPase. Interestingly, only after phosphorylation of the enzyme do the susceptible bond(s) which lead to the loss of occlusion become exposed to trypsin.
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PMID:Uncoupling of occlusion from ATP hydrolysis activity in sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase. 800 38