| Summary: | 碩士 === 朝陽科技大學 === 應用化學系碩士班 === 93 === Tyrosine phosphorylation is one of the key covalent modifications that occurs in multicellular organisms as a result of intercellular communication during embryogenesis and maintenance of adult tissues. The enzymes that carry out this modification are the protein tyrosine kinases (PTKs), which catalyze the transfer of the γ phosphate of ATP to tyrosine residues on protein substrate. Phosphorylation of tyrosine residues modulates enzymatic activity and creates binding sites for the recruitment of downstream signaling proteins. Since PTKs are critical components of cellular signaling pathways, high-resolution structural studies of PTKs will provide a molecular basis for understanding the mechanisms by which PTKs are regulated.
Human’s spleen tyrosine kinases (SYK) is one kind of PTKs, and contains 635 residues. The kinase domain of SYK is composed of 267 residues, from serial number 370 to 635. Renumber it as 1 to 267. Tyrosine 156 and tyrosine 157 (Y156 and Y157) play important roles in the phosphorylation, therefore, we concentrated the structure analysis of a synthesized, 16-residued fragment of SYK, whose primary structure is NH2-Lys-Ala-Leu-Arg-Ala-Asp-Glu-Asn-Tyr-Tyr-Lys-Ala-Gln-Thr-His-Gly
-OH.
Our results of Homology Modeling and CD, NMR experiments show that the conformation of this Y156 and Y157 centered fragment in aqueous solution is random coil, and it is ��-strand in dimethyl sulfoxide (DMSO).
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