Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The palmitoylation site of the membrane glycoprotein E1 of Semliki Forest virus (SFV) has been identified by chemical analysis of an acylpeptide. 3H-Palmitoylated E1 isolated from SFV grown in baby hamster kidney cells was digested with chymotrypsin and the resulting peptides subjected to high performance liquid chromatography on a wide-pore column. The 3H-acylated peptide fraction peaked at above 60% 2-propanol in the eluent, indicating its hydrophobic character. Polyacrylamide gel electrophoresis analysis revealed a molecular weight of about Mr = 6000 for the radiolabeled peptide. Manual sequencing of this material by the 4-N,N'-dimethylaminoazobenzene-4'-isothiocyanate/phenylisothiocyanate procedure on solid phase revealed the amino-terminal sequence Ala-Ala-Ser-His-Ser-Asn-Val-Val-Phe-Pro. The same peptide also labels with [35S]cysteine. Comparison with the deduced amino acid sequence of E1 revealed that the palmitoylated peptide contains at least 43 amino acid residues, and thus includes the membrane spanning region down to the only cysteine residue five positions up from the carboxyl terminus of E1. Since [3H]palmitic acid was cleaved from E1 with thiol reagents, and since the peptide labels with [14C]iodoacetamide only after the release of fatty acids by hydroxylamine treatment, cysteine in position 433 represents the palmitoylation site in SFV E1.
 ...
PMID:Chemical identification of cysteine as palmitoylation site in a transmembrane protein (Semliki Forest virus E1). 314 15

A preparation of peptidyl-tRNA from intact microsomes of mucin-synthesizing polysomes of sublingual salivary gland cells contained fatty-acylated galactosamine-free and galactosamine-enriched peptidyl-tRNA fractions, whereas trypsin-chymotrypsin treated microsomes yielded predominantly the acylated galactosamine-enriched peptidyl-tRNA complexes. Radioscanning and chemical analyses revealed that palmitate was substituted on all nascent peptides, except those shorter than 20 amino-acid residues. In contrast, the [35S]-methionine label was detected only on galactosamine-free peptides containing up to 70 amino acids. On SDS-polyacrylamide gel, the peptides released from galactosamine-enriched tRNA complexes separated into a multitude of bands ranging in size from 6000 to 60,000 dalton, whereas the total preparation afforded peptides ranging from 2000 to 60,000 dalton. Pulse-chase experiments, using radiolabelled methionine, palmitic acid and N-acetylgalactosamine, combined with chemical characterization of the radiolabelled fatty acids and carbohydrates from purified peptidyl-tRNA, confirmed that the N-terminal fatty acylation and the initial O-glycosylation with N-acetylgalactosamine are the co-translational processes taking place as soon as peptide is sufficiently large to be acylated, trimmed, and translocated to the luminal site of endoplasmic membrane.
 ...
PMID:Co-translational processing and intracellular transport of rat salivary mucus glycoprotein. 325 86

We have studied the synthesis and expression of surface proteins in zygotes of Plasmodium gallinaceum during their transformation to mature ookinetes. The cells were biosynthetically labelled in vitro using [35S]methionine and proteins were immunoprecipitated with rabbit anti-ookinete serum or monoclonal antibodies. Early zygotes (approx. 2 h post-gametogenesis and fertilization) synthesized and expressed on their surface a protein of Mr 26 000 as observed under reducing conditions on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) (31 000 under non-reducing conditions) and continued to do so for 8-10 h; thereafter synthesis of the Mr 26 000 protein declined and little or none was synthesized in the mature ookinetes (greater than 20 h post-gametogenesis). Between 3-5 h post-gametogenesis, zygotes also began to synthesize a protein of Mr 28 000 (34 000 under non-reducing conditions). Synthesis and expression of this surface protein continued throughout development; and the Mr 28 000 protein was the predominant surface protein synthesized by the mature ookinete. Mr 26 000 and Mr 28 000 proteins have been designated earlier as PgO-1 and PgO-2 respectively (Carter and Kaushal, Mol. Biochem. Parasitol. (1984) 13, 235-241). Neither protein was synthesized in the gametocytes prior to gametogenesis. Both proteins could be labelled with [3H]glucosamine or [3H]mannose. When zygotes were incubated with [3H]palmitic acid both PgO-1 and PgO-2 bound fatty acids in covalent linkage. The two proteins do not otherwise appear to be structurally related. They were differentially immunoprecipitated by different monoclonal antibodies and gave rise to distinct patterns of peptides following digestion with proteases such as Staphylococcus aureus V-8, trypsin and chymotrypsin.
 ...
PMID:Biosynthesis of two stage-specific membrane proteins during transformation of Plasmodium gallinaceum zygotes into ookinetes. 403 6

Mumps virus strains differ in their ability to induce cell fusion following an infection: strains with active neuraminidase (NANase) fail to cause cell fusion, while strains with less active NANase cause cell fusion. When chymotrypsin is added to infected cells, cell fusion is amplified in a concentration-dependent manner for all mumps virus strains. Virions produced in such infections do not express HN glycoprotein-associated activities. Chymotrypsin treatment of purified mumps virus in vitro results in sequential cleavage of the HN glycoprotein without affecting F glycoprotein structure. Initially, HN is cleaved into two glycopolypeptides, HNc1 (32K) and HNc2' (41K), with concomitant loss of hemagglutinating and NANase activities, and infectivity. Further incubation with chymotrypsin causes complete degradation of HNc1 and digestion of HNc2' to HNc2 (13K-19K). Both HNc2' and HNc2 contain the [3H]palmitic acid label found in the HN polypeptide, which suggests that these fragments are associated with the viral membrane. Analyses of infected cells and released virions indicate that chymotrypsin acts similarly on HN exposed at the cell surface. Exogenous NANase does not abolish the protease-augmented cell fusion, though it does reduce cell fusion of untreated fusing strain infections. These results confirm that mumps virus HN glycoprotein is critically linked to cell fusion cytopathology and show that cryptic cell fusion activity in nonfusing strain infections can be unmasked by the proteolytic removal of the HN glycoprotein.
 ...
PMID:Conversion of nonfusing mumps virus infections to fusing infections by selective proteolysis of the HN glycoprotein. 636 84

alpha-Actinin has been proposed to be the actin-plasma membrane linker. This assumption is based on the discovery of direct interaction of alpha-actinin with two specific lipids, diacylglycerol and palmitic acid [Burn, P. (1988) Trends Biochem. Sci. 13, 79-83]. In our study, the binding of alpha-actinin with vesicles containing negatively charged phospholipids was measured by the method of 90 degrees light-scattering. Our results show that alpha-actinin is able to bind membranes containing negatively charged phospholipids, but not to bind membranes composed of neutral lipids only. Diacylglycerol and palmitic acid, on the other hand, have little effect on the binding of alpha-actinin to lipid vesicles. Analysis of binding isotherms in terms of a membrane binding model gave apparent dissociation constants which varied between 0.2 and 3 microM over a range of 5-20 mol % negatively charged phospholipid. Comparing the kinetics of alpha-chymotrypsin digestion of alpha-actinin in solution to those of vesicle-bound alpha-actinin, it can be seen that the cleavage site at the junction between the C-terminal and the central rod domain of alpha-actinin and another cleavage site on the C-terminal domain can be most effectively protected by its membrane binding. Analysis of the amide I and II regions of Fourier-transform infrared spectra of alpha-actinin revealed that the association of alpha-actinin with negatively charged phospholipid vesicles resulted in some perturbation of the protein secondary structure. Monolayers containing negatively charged phospholipid were layered and incubated on the surface of a polymerization solution of actin and alpha-actinin, and observed with an electron microscope. The results show that the bundle structure of actin filaments can be formed if diacylglycerol and palmitic acid are present in lipid layers.
 ...
PMID:Interactions between smooth muscle alpha-actinin and lipid bilayers. 926 16