Threonine, structure

This interpretation of the base-catalyzed P-elimination of the glycan part from glycosyl serine and threonine structures, in turn, initiated the idea to utilize these... 

Figure 4.4 Schematic diagram of the structure of the a/p-barrel domain of the enzyme methylmalonyl-coenzyme A mutase. Alpha helices are red, and p strands are blue. The inside of the barrel is lined by small hydrophilic side chains (serine and threonine) from the p strands, which creates a hole in the middle where one of the substrate molecules, coenzyme A (green), binds along the axis of the barrel from one end to the other. (Adapted from a computer-generated diagram provided by P. Evans.)...

In both structures the ion is coordinated to six ligands with octahedral geometry. Four water molecules as well as the side chain oxygen atom of a serine residue from the P-loop and one oxygen atom from the (3-phosphate bind to Mg + in the GDP structure. Two of the water molecules are replaced in the GTP structure by a threonine residue from switch I and an oxygen atom from the y phosphate (similar to the arrangement shown in... 

Now, it is seen that polar groups dominate the molecular structure, resulting from hydroxyl groups from the two serine and threonine fragments in addition to the peptide bonds themselves. Only weak dispersive interactions will be contributed by glycine fragments (CH2 groups). 

FIGURE 4.14 The stereoisomers of isoleucine and threonine. The structures at the far left are the naturally occurring isomers. 

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. 

Threonine, stereoisomers of, 302-303 structure and properties of, 1019 Threose. configuration of, 982 molecular model of, 294 Thromboxane B2. structure of,... 

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. 

Figure 52-6. Diagrammatic representation of the structures of the H, A,and B blood group substances. R represents a long complex oligosaccharide chain, joined either to ceramide where the substances are glycosphingolipids, or to the polypeptide backbone of a protein via a serine or threonine residue where the substances are glycoproteins. Note that the blood group substances are biantenna ry ie, they have two arms, formed at a branch point (not indicated) between the GIcNAc—R, and only one arm of the branch is shown. Thus, the H, A,and B substances each contain two of their respective short oligosaccharide chains shown above. The AB substance contains one type A chain and one type B chain.

The structures predicted for the fast and slow Ca -ATPase (Fig. 1) are 84 /o identical [8], There are 164 differences in the amino acid sequences between the two isoenzymes, 66 of which are conservative replacements, involving substitution of serine for threonine, aspartic for glutamic, lysine for arginine, or interchanges between aromatic or hydrophobic amino acids [8],... 

---