Three- threonines

Lysine (AAA, AAG), glutamine, and cysteine have two codons isoleucine, leucine and phenylalanine have three threonine, glycine, alanine, valine, proline, and tyrosine all have four and serine and arginine have six. Consequently, in many cases more than one codon is able to dictate the position of a given amino acid. The code is therefore referred to as a degenerate code. As a result, many mutations occur which are not accompanied by alterations in the amino acid sequence. It would therefore appear that a degenerate code constitutes an evolutionary advantage, and even if all 64 triplets existed in the RNA template, all triplets need not function in transcription. The choice of a triplet could also be restricted by the number of available transfer RNA s. But if 60 sequences can be used... 

Reinscheid, D., Kircher, M., and Sahm, H. (1991) Amplification of three threonine biosynthesis genes in Corynehacterium glutamicum and its... 

Fig. 1. Amino acid sequence for the A- and B-chains of human iasulin [11061-68-0] where soHd lines denote disulfide bonds. Porciae iasulin [12584-58-6] differs by one amino acid ia the B-chaia where alanine replaces threonine at positioa 30. Boviae iasulia [11070-73-8] differs by three amino acids. la the A-chain alanine replaces the threonine at positioa 8 and valine replaces the isoleuciae at position 10. In the B-chain there is an alanine at position 30.

How would substrate preference be changed if the glycine residues in trypsin at positions 216 and 226 were changed to alanine rather than to the more bulky valine and threonine groups that are present in elastase This question was addressed by the groups of Charles Cralk, William Rutter, and Robert Fletterick in San Francisco, who have made and studied three such trypsin mutants one in which Ala is substituted for Gly at 216, one in which the same substitution is made at Gly 226, and a third containing both substitutions. 

FIGURE 9.26 The carbohydrate tnoiedes of glycoproteins may be linked to the protein via (a) serine or threonine residues (in the O-linked saccharides) or (b) asparagine residues (in the N-linked saccharides), (c) N-Linked glycoproteins are of three types high mannose, complex, and hybrid, the latter of which combines structures found in the high mannose and complex saccharides. 

Third law of thermodynamics A natural law that states that the entropy of a perfectly ordered, pure crystalline solid is 0 at 0 K Thomson, J. J., 25 Three Mile Island, 525-526 Threonine, 622t Tin... 

MAPK cascades are composed of three cytoplasmic kinases, the MAPKKK, MAPKK, and MAPK, that are regulated by phosphorylation (Fig. 1) [1, 2]. The MAPKKK, also called MEKK for MEK kinase, is a serine/threonine kinase. Selective activation of MAPKKKs by upstream cellular stimuli results in the phosphorylation of MAPKK, also called MEK for MAP/ERK kinase by the MAPKKK. MAPKKK members are structurally diverse and are differentially regulated by specific upstream stimuli. The MAPKK is phosphorylated by the MAPKKK on two specific serine/ threonine residues in its activation loop. The MAPKK family members are dual specificity kinases capable of phosphorylating critical threonine and tyrosine residues in the activation loop of the MAPKs. MAPKKs have the fewest members in the MAPK signaling module. MAPKs are a family of serine/threonine kinases that upon activation by their respective MAPKKs, are capable of phosphorylating cytoplasmic substrates as well as... 

Peptidases have been classified by the MEROPS system since 1993 [2], which has been available viatheMEROPS database since 1996 [3]. The classification is based on sequence and structural similarities. Because peptidases are often multidomain proteins, only the domain directly involved in catalysis, and which beais the active site residues, is used in comparisons. This domain is known as the peptidase unit. Peptidases with statistically significant peptidase unit sequence similarities are included in the same family. To date 186 families of peptidase have been detected. Examples from 86 of these families are known in humans. A family is named from a letter representing the catalytic type ( A for aspartic, G for glutamic, M for metallo, C for cysteine, S for serine and T for threonine) plus a number. Examples of family names are shown in Table 1. There are 53 families of metallopeptidases (24 in human), 14 of aspartic peptidases (three of which are found in human), 62 of cysteine peptidases (19 in human), 42 of serine peptidases (17 in human), four of threonine peptidases (three in human), one of ghitamicpeptidases and nine families for which the catalytic type is unknown (one in human). It should be noted that within a family not all of the members will be peptidases. Usually non-peptidase homologues are a minority and can be easily detected because not all of the active site residues are conserved. 

Similar experiments suggested that 4-hydroxy-L-threonine (43) was an intermediate in synthesis of the three-carbon unit, C-6, C-5, C-5 (after decarboxylation). This was rigorously proved by a chemical synthesis of 4-hydroxy-L-(2,3-13C2)threonine. Incubation of E. coli mutant WG2 with this substrate produced a sample of pyridoxol that was examined by l3C NMR. The presence of doublets in the signals originating from C-5 and C-6 of pyridoxol exclusively, showed that the C-2-C-3 bond of the substrate had been incorporated intact into the predicted site (Scheme 18).42... 

It was straightforward to identify the spin systems of four valines, five threonines, four alanines, three glycines, two glutamates, and AMX type residues (Asp, Cys, Phe, Tyr, Trp, and Ser) of this protein from the COSY, RELAY, and NOESY spectra in D O solution. The RELAY spectrum was particularly useful in identification of Val, Ala, Thr, and Glu spin systems. 

Removal of the oligosaccharide chain from the glycoprotein usually involves the use of one of three main methods treatment with NaOH-NaBH4, hydrazinolysis, or proteolysis.34-36 The NaOH-NaBH4 treatment is used to release, somewhat specifically, oligosaccharides O-linked to serine and threonine. Hydrazinolysis is used to break N-linkages, and proteolysis, to isolate glycopeptides. Each method apparently still has some drawbacks. 

Protein kinase B, or Akt, was discovered as the product of an oncogene of the acutely transforming retrovirus AKT8, causing T-cell lymphomas in mice. It encodes a fusion product of a cellular serine/threonine protein kinase and the viral structural protein Gag. This kinase is similar to both protein kinase Ce (PKCe 73% identity to the catalytic domain) and protein kinase A (PKA 68%). It differs from other protein kinases in that it contains a pleckstrin homology (PH) domain, which allows it to bind to polyphosphoinositide head groups (and also to G-protein fly subunits). To date, three subtypes have been identified a, (3, and y, all of which show a broad tissue distribution. It... 

The catechol-type ligand appears to be restricted to siderochromes derived from prokaryotic microorganisms. Klebsiella oxytoca, an organism closely related to members of the genus Aerobacter, forms the 2,3-dihy-droxy-N-benzoyl derivates of serine and threonine in three day cultures (72). It is not known if the latter amino acid occurs in trimers but examination of space-filling CPK models does indicate that enterobactin could accomodate a methyl substituent on the carbon of the serine residue. Catechols occur in higher protist organisms but their formation... 

Scheme 1 summarizes our synthetic approach. By protecting the carboxyl groups using a suitable protecting group, the three hydroxy amino acids, serine, threonine and tyrosine were conveniently coupled with Boc-Phe-OH to obtain the corresponding peptides (1-4) in good yields. 

Three levels of SEA are presented in the graph for each amino acid, which corresponds to areas in A2 accessible to the solvent environment greater than 30 A2 for highly accessible amino acids, between 10 and 30A2 for medium accessibility, and less than 10 A2 for those residues that are relatively not accessible to the solvent. Only the SEA for each amino acid of >30A2 is shown in the plotted data. The graph shows that the polar amino acids such as serine, threonine,... 

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