| protein-S-isoprenylcysteine O-methyltransferase | <enzyme> Methylates carboxyl-terminal cysteine of yeast sex factors and ha-ras oncogene protein; c-terminal s-geranylgeranylcysteine and s-geranylcysteine residues are also methylated more slowly Registry number: EC 2.1.1.100 Synonym: pcc methyltransferase, farnesyl cysteine c-terminal methyltransferase, protein-cysteine-carboxyl methyltransferase, 5-prenylcysteine methyltransferase, isoprenylated protein methyltransferase, ste14 gene product, prenylated protein carboxyl methyltransferase, ppmtase, protein c-terminal prenylcysteine methyltransferase (26 Jun 1999) |
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| protein splicing | Excision of in-frame internal protein sequences (inteins) of a precursor protein, coupled with ligation of the flanking sequences (exteins). Protein splicing is an autocatalytic reaction and results in the production of two proteins from a single primary translation product: the intein and the mature protein. (12 Dec 1998) |
| protein status | A term used to indicate the level of protein in a person's system. A severe lack of protein can result in protein-calorie malnutrition. (16 Dec 1997) |
| protein structure | The amino acids and their manner of arrangement in constituting a protein. The four stages of protein structuring are primary (protein structure, primary see amino acid sequence), secondary (protein structure, secondary), tertiary (protein structure, tertiary), and quaternary (protein structure, quaternary see protein conformation). (12 Dec 1998) |
| protein structure, secondary | The stage in the development of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices and beta sheets. This is the first folding level of protein building. (12 Dec 1998) |
| protein structure, tertiary | The stage in the structural development of a protein in which combinations of alpha helices and beta sheets pack together to form compactly folded globular units named domains. Small proteins consist of only one domain but larger proteins contain a number of domains which are usually connected by open lengths of polypeptide chain. This stage is a combination of the second and third folding levels of protein building. (12 Dec 1998) |
| protein synthesis | The process in which individual amino acids, whether of exogenous or endogenous origin, are connected to each other in peptide linkage in a specific order dictated by the sequence of nucleotides in DNA; this governing sequence is conveyed to the synthesizing apparatus in the ribosomes by mRNA, formed by base-pairing on the DNA template. (05 Mar 2000) |
| protein synthesis inhibitor | Compounds which inhibit the synthesis of proteins. They are usually antibiotics or toxins. Mechanism of the action of inhibition includes the interruption of peptide-chain elongation, the blocking the the a site of ribosomes, the misreading of the genetic code or the prevention of the attachment of oligosaccharide side chains to glycoproteins. (12 Dec 1998) |
| protein targeting | The process through which newly-made proteins are sorted and carriedto different parts of a cell. (09 Oct 1997) |
| protein-tyrosine kinase | <enzyme> An enzyme that catalyses the phosphorylation of tyrosine residues in proteins with ATP or other nucleotides as phosphate donors.12. Chemical name: ATP:protein-tyrosine O-phosphotransferase Registry number: EC 2.7.1.112 (12 Dec 1998) |
| protein-tyrosine-phosphatase | <enzyme> An enzyme group that specifically dephosphorylates phosphotyrosyl residues in selected proteins. Together with protein-tyrosine kinase, it regulates tyrosine phosphorylation and dephosphorylation in cellular signal transduction and may play a role in cell growth control and carcinogenesis. Chemical name: Protein-tyrosine-phosphate phosphohydrolase Registry number: EC 3.1.3.48 (12 Dec 1998) |
| protein Zero | <protein> The major glycoprotein of peripheral nerve myelin, an integral transmembrane protein, synthesised by Schwann cells (Mw = 28, 500). (18 Nov 1997) |
| proteolipid protein | <protein> Highly conserved membrane protein (30 kD) in myelin. Cellular function obscure but mutations lethal for example jimpy mouse and Pelizaeus Merzbacher disease of man. (18 Nov 1997) |
| proto-oncogene protein p21(ras) | Cellular protein encoded by the c-ras genes. The protein has GTPase activity and is involved in transmembrane signal transduction as a guanine nucleotide binding protein. Elevated levels of p21 c-ras have been associated with neoplasia. (12 Dec 1998) |
| proto-oncogene protein pp60(c-src) | <enzyme> Membrane-associated tyrosine-specific kinase encoded by the c-src genes. It has an important role in cellular growth control. Truncation of carboxy-terminal residues in pp60(c-src) leads to pp60(v-src) which has the ability to transform cells. This kinase pp60 c-src should not be confused with csk, also known as c-src kinase. Registry number: EC 2.7.1.- (12 Dec 1998) |