| Autor: |
Tomasselli, Alfredo G., Marquetant, Rainer, Noda, Lafayette H., Goody, Roger S. |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; 7/16/84, Vol. 142 Issue 2, p287-289, 3p |
| Abstrakt: |
The diastereomers of adenosine 5′-O-[l-thio]triphosphate (ATP[αS]) and adenosine 5′-O-[2qhio]triphosphate (ATP[βS]) were utilized to seek unambiguous assignment of Mg2+ coordination to ATP when bound to ATP-AMP phosphotransferase from beef heart mitochondria (AK2). Similarly, the diastereomers of guanosine 5′-O-[thio]triphosphate (GTP[αS]) and guanosine 5′-O-[2-thio]triphosphate (GTP[βS]) were utilized to seek unambiguous assignment of Mg2+ coordination to GTP when bound to GTP-AMP phosphotransferase from beef heart mitochondria (AK3). Furthermore the diastereomers of guanosine 5′-O-[l-thio]diphosphate (GDP-[αS]) have been used to assign Mg2+ coordination to GDP when bound to AK3. The ratios ( V for isomer Sp)/( V for isomer Rp) obtained in the presence of Mg2+ and Cd2+ are compared to those already published for ATP-AMP phosphotransferases from pig muscle (AK1) [Kalbitzer et al. (1983) Eur. J. Biochem. 133, 221–227] and from baker's yeast (AKy) [Tomasselli and Noda (1983) Eur. J. Biochem. 132, 109–115]. In all cases, coordination of Mg2+ to the β-phosphate via the pro-R oxygen is present, as shown by reversal of specificity for the diastereomers of ATP[βS] or GTP[βS] respectively on changing the metal ion. In contrast, there is no reversal of specificity for the diastereomers of ATP[αS] or GTP[αS], or for GDP[αS] in the case of AK3 for the reverse reaction, indicating that there is no interaction of the metal with the α-phosphate group. The observed stereospecifity for the α-thiophosphate is consistent with the assumption of an interaction of the pro-R oxygen of the α-phosphate group with the enzyme. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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