| Autor: |
Oikonomakos NG; Laboratory of Molecular Biophysics, University of Oxford, U.K., Johnson LN, Acharya KR, Stuart DI, Barford D, Hajdu J, Varvill KM, Melpidou AE, Papageorgiou T, Graves DJ, et. al. |
| Jazyk: |
angličtina |
| Zdroj: |
Biochemistry [Biochemistry] 1987 Dec 15; Vol. 26 (25), pp. 8381-9. |
| DOI: |
10.1021/bi00399a053 |
| Abstrakt: |
The detailed environment of the essential cofactor pyridoxal 5'-phosphate in glycogen phosphorylase b, resulting from crystallographic refinement at 1.9-A resolution, is described. The pyridoxal ring is buried in a nonpolar site containing three aromatic rings while the 5'-phosphate group is highly solvated and makes only three direct contacts to the protein. The pyridine nitrogen interacts via a water with protein atoms [main chain carbonyl oxygen (Asn-133) and OH of tyrosine (Tyr-90)]. The crystal structures of three active derivatives of phosphorylase reconstituted with 5'-deoxypyridoxal 5'-methylenephosphonate (PDMP), 6-fluoropyridoxal 5'-phosphate (6-FPLP), and pyridoxal (PL) in place of the natural cofactor have been determined at 2.5-A resolution. The results for PDMP-phosphorylase show a closer proximity of the phosphonate group to the NZ atom of a lysine (Lys-574) than that observed in the native enzyme, consistent with 31P NMR studies that have shown a change in ionization state of the phosphonate group compared to the native cofactor phosphate. The replacement of the polar 5'-ester linkage by a CH2 group results in a small shift of a water and its hydrogen-bonded tyrosine (Tyr-648). In 6-FPLP-phosphorylase the fluorine is accommodated with no significant change in structure. It is suggested that substitution of the electronegative fluorine at the 6-position may result in lower activity of 6-FPLP-phosphorylase through a strengthening of hydrogen-bonded interactions to the pyridine nitrogen N1.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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