Regulatory phosphorylation sites

Muscle glycogen phosphorylase is a dimer of two identical subunits (842 residues, 97.44 kD). Each subunit contains a pyridoxal phosphate cofactor, covalently linked as a Schiff base to Lys °. Each subunit contains an active site (at the center of the subunit) and an allosteric effector site near the subunit interface (Eigure 15.15). In addition, a regulatory phosphorylation site is located at Ser on each subunit. A glycogen-binding site on each subunit facilitates prior association of glycogen phosphorylase with its substrate and also exerts regulatory control on the enzymatic reaction. 

Pickham, K. M., Meyer, A. N., Li, J and Donoghue, D. J. (1992). Requirement of mosx protein kinase for meiotic maturation of Xenopus oocytes induced by a cdc2 mutant lacking regulatory phosphorylation sites. Mol. Cell. Biol. 12 3192-3203. 

Hentschel, P, Krucker, M., Grynhaum, M. D., Putzhach, K., Bischoff, R., and Albert, K., Determination of regulatory phosphorylation sites in nanogram amounts of a synthetic fragment of ZAP-70 using microprohe NMR and on-hne coupled capillary HPLC-NMR, Magnetic Resonance in Chemistry 43(9), 747-754, 2005. 

Ser and Thr residues that serve as regulatory phosphorylation sites. Mutations are also described for these regions leading to oncogenic activation of Raf kinase. The protein kinase activity is found in the CR3 domain. 

Munday, M.R. Campbell, D.G. Carling, D. Hardie, D.G. Identification by amino acid sequencing of three major regulatory phosphorylation sites on rat acetyl-CoA carboxylase. Eur. J. Biochem., 175, 331-338 (1988)... 

Jiao, J., Vidal, J., Echevarria, C. Chollet, R. (1991). In vivo regulatory phosphorylation site in C4-leaf phosphoeno/pyruvate carboxylase from maize and sorghum. Plant Physiology 96, 297-301. 

Obermann, W. M., Gautel, M., Weber, K., and Furst, D. O. (1997). Molecular structure of the sarcomeric M band Mapping of titin and myosin binding domains in myomesin and the identification of a potential regulatory phosphorylation site in myomesin. EMBOJ. 16, 211-220. 

Douglas, P., Morrice, N., and MacKintosh, C., 1995, Identification of a regulatory phosphorylation site in the hinge 1 region of nitrate reductase from spinach (Spinacea oleracea) leaves, FEES Lett. 177 11311117. 

These observations and mutation studies have shown that the activity of c-Src kinase is subject to strict regulation. The domain structure of c-Src kinase is shown in Fig. 8.17a. Src kinase carries a myristinic acid residue as a membrane anchor and harbors an SH2 and an SH3 domain N-terminal to its kinase domain. Furthermore, Src kinase possesses two important regulatory phosphorylation sites, namely Tyr 416 in the activation loop and Tyr 527 near the C-terminus. 

The y-isoenzyme lacks the C2 domain, is prenylated at the C-terminus, and lacks the regulatory phosphorylation sites of cPLAja. The enzyme demonstrates high lysophospho-lipase activity and lacks the acyl chain selectivity of the a-isoenzyme suggesting a role in phospholipid remodeling [23]. The 6, e, and -isoezymes have been identified more recently (H. Chiba, 2004 T. Ohto, 2005) and are discussed [23]. The group IV isoenzymes (a- ) have also been designated A-F [15]. 

When in the presence of endogenous currents, the presence or absence of subunits (directly associated regulatory proteins) and kinases or phosphatases controlling regulatory phosphorylation sites can affect the pharmacology of the expressed channel protein relative to native cardiac ion channels. 

Segment V is the variable, COOH-terminal portion of the molecule containing regulatory phosphorylation sites. The mammalian muscle isoform has 7 sites, the liver isoform 5 and the yeast Gsy2p 3 sites. Two of the yeast sites can readily be seen as conserved versions of mammalian sites 3a and 3b. It is possible that the yeast and mammalian enzymes share some phosphorylation controls but not others. 

C. Characterization of Regulatory Phosphorylation Sites 0. Phosphoamino Acids Involved in MetaHon Binding... 

Two different models have been proposed to explain how regulatory phosphorylation sites may exert their function. Either the dianionic phosphoserine is salt-linked to an arginine or lysine residue and in doing so may help stabilize one spedfic protein conformation, or a mobile phosphoryl group may prevent an interaction between protein domains. In the latter case, one would expect the resonance to show titration behavior with a Hill coefficient similar to that of standards, which is indeed observed for some of the proteins. When salt bridges play a role, the energy involved has to be <5 kcal mol in order to observe a titration behavior. A lower pA, and an increased Hill coeffident (n > 1) can provide evidence for the presence of proximal positive charges. 

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