Tyrosine polypeptide

The polypeptide chain of Src tyrosine kinase, and related family members, comprises an N-terminal "unique" region, which directs membrane association and other as yet unknown functions, followed by a SH3 domain, a SH2 domain, and the two lobes of the protein kinase. Members of this family can be phosphorylated at two important tyrosine residues—one in the "activation loop" of the kinase domain (Tyr 419 in c-Src), the other in a short... 

C-terminal tail (Tyr 527 in c-Src). Phosphorylation of Tyr 419 activates the kinase phosphorylation of Tyr 527 inhibits it. Crystal structures of a fragment containing the last four domains of two members of this family were reported simultaneously in 1997—cellular Src by the group of Stephen Harrison and Hck by the group of John Kuriyan. The two structures are very similar, as expected since the 440 residue polypeptide chains have 60% sequence identity. The crucial C-proximal tyrosine that inhibits the activity of the kinases was phosphorylated in both cases the activation loop was not. 

Neuropeptide Y (NPY) is a 36 amino acid polypqrtide with tyrosine residues at both ends of the molecule. It is characterised structurally by a PP-fold consisting of an extended polyproline helix and an a-helix connected by a (3-tum [1]. Based on structural and evolutionary criteria, NPY is closely related to peptide YY (PYY) and pancreatic polypeptide (PP). 

HSFl phosphorylation must be sensitive to nonheat inducers of HSF-DNA binding activity because HSFl phosphorylation can be achieved at 37 °C by other inducers of the HS response. HSF 1 contains polypeptide sequences that could serve as substrates for well characterized protein kinases, but few of these are known to be heat inducible. One family of protein kinases, the S6 protein kinases, have already been shown to exhibit heat inducible activity however, their peak level of activity during HS occurs well after the maximal induction of HSF phosphorylation (Jurivich et al., 1991). Thus, other protein kinases are likely to be directly linked to the phosphorylation of HSF. Some of the putative protein phosphorylation sites on HSF include motifs for protein kinase C, casein kinase, and enterokinase. There are tyrosine sequences that match substrates for known tyrosine kinases, but whether these residues are accessible to phosphorylation is not established. 

In the Fepr protein the two clusters are some 12-13 A apart and probably within electron transfer range. However, as shown in Fig. 15, there are no obvious electron pathways involving the polypeptide chain. A tyrosine residue, Tyr 493, lies approximately midway be-... 

Kentolysin Compared to Heliantholysin. Stoichactis helianthus occurs in the Caribbean region whereas another species, Stoichactis kenti is distributed in the Indo-Pacific area. The latter produces a toxin, kentolysin, that is similar to, but not identical with heliantholysin (6). The amino acid compositions of the two polypeptides show a distinct resemblance but appear to differ significantly in number of residues of lysine, methionine, tyrosine and histidine. IgG from a rabbit immunized against heliantholysin neutralizes both heliantholysin and kentolysin, but neutralization of the homologous toxin is more efficient (Table III). It can be seen that in the concentrations used, the IgG failed to neutralize the related lytic peptides of Condylactis gigantea and Epiactis prolifera. 

The most potent thrombin inhibitor is hirudin, originally isolated from the salivary glands of the medicinal leech Hirudo medicinalis. Its inhibition constant is in the femtomolar (10-15 M) range (57). It is a 65-amino-acid tyrosine-sulfated single-chain polypeptide. Recombinant hirudin differs from native hirudin by the absence of the sulfate group on tyrosine 63 (Tyr-63) and is referred to as desulfato hirudin. The loss of this sulfate group reduces the thrombin inhibitory potency by 10-fold. 

IL-ll is a 23 kDa, 178 amino acid polypeptide. Its receptor appears to be a single-chain 150 kDa transmembrane protein. Binding of IL-ll results in tyrosine phosphorylation of several intracellular proteins, which, in turn, somehow promote the observed biological activities of IL-ll. 

The presence of an anticoagulant in the saliva of the leech, Hirudo medicinalis, was first described in 1884. However, it was not until 1957 that the major anticoagulant activity present was purified and named hirudin. Hirudin is a short (65 amino acid) polypeptide, of molecular mass 7000 Da. The tyrosine residue at position 63 is unusual in that it contains a sulfate group. The molecule appears to have two domains. The globular N-terminal domain is stabilized by three disulfide linkages, whereas the C-terminal domain is more elongated and exhibits a high content of acidic amino acids. 

The number of neural genes known to contain CREs is growing as more and more genes are cloned. Prominent examples are tyrosine hydroxylase, c-fos, proenkephalin, prodynorphin, somatostatin and vasoactive intestinal polypeptide (VIP). Expression of these genes has been... 

G3. GoiSon, M. R., Determination colorimetrique de l index-tyrosine des polypeptides urinaires. Bull. soc. chim. biol. 16, 1686-1091 (1934). 

Chymotrypein is a proteolytic and milk-curdling enzyme of the pancreatic secretion. It is a protein endopeptidase which catalyses the hydrolysis of native proteins to peptones, polypeptides and amino acids, by breaking the peptide linkages of the carboxyl groups of tyrosine and phenylalanine. 

Tyrosine Fluorescence and Phosphorescence from Proteins and Polypeptides... 

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