Thiophosphate analogs of ADP and ATP as substrates in partial reactions of energy conversion in chloroplasts |
| |
Authors: | H Strotmann S Bickel-Sandkötter K Edelmann F Eckstein E Schlimme KS Boos J Lüstorff |
| |
Institution: | 1. Botanisches Institut, Abteilung für Biochemie der Pflanzen, Tierärztliche Hochschule Hannover, F.R.G.;2. Max-Planck-Institut für Experimentelle Medizin, Abteilung Chemie, Göttingen, F.R.G.;3. Fachgebiet Organische Chemie im Fachbereich Naturwissenschaften, Gesamthochschule Paderborn, F.R.G.;4. Institut für Klinische Biochemie und Physiologische Chemie, Medizinische Hochschule Hannover, Hannover F.R.G. |
| |
Abstract: | Thiophosphate analogs of ADP and ATP have been employed in partial reactions of photosynthetic energy conversion in chloroplasts. Substitution of oxygen by sulfur at the α-phosphate yields a pair of diastereomers (ADPαS, ATPαS, A and B forms). Two diastereomeric compounds are also obtained by replacement of oxygen by sulfur in the β-phosphate group of ATP (ATPβS, A and B form) (Eckstein, F. and Goody, R.S. (1976) Biochemistry 15, 1685–1691).The A form of ADPαS is phosphorylated by chloroplasts with a Km comparable to that of ADP but with a lower V. The B form of ADPαS as well as ADPβS is not a substrate in photophosphorylation and only weakly competes with ADP.The A forms of ADPαS and ATPαS strongly compete with ADP for the tight nucleotide binding site of CF1 in the light-induced exchange reaction, whereas the B forms display a much smaller competitive effect. The efficiencies of ADPβS and the A isomer of ATPβS are intermediate, and the B form of ATPβS is a weaker competitor.The A forms of ATPαS and ATPβS are hydrolyzed by light-triggered ATPase, whereas the B forms are not. The efficiency of the A isomer of ATPαS is comparable to that of normal ATP, and the A form of ATPβS is cleaved at a lower rate. In trypsin-activated Ca2+-dependent ATPase the A form of ATPαS is the only thiophosphate analog to be hydrolyzed.The results indicate a stereospecific interaction of ADP and ATP at the catalytic sites as well as the tight nucleotide binding site of coupling ATPase of chloroplasts. |
| |
Keywords: | Photophosphorylation ATPase Nucleotide binding Thiophosphate nucleotide analogs (Chloroplast) ADPαS ATPαS ADPβS ATPβS Plasmocorinth B 3-(5-chloro-2-hydroxyphenylazo)-4 5-dihydroxy-2 7-naphthalenedisulfonic acid Tricine tris-(hydroxymethyl)-methylglycine chloroplast coupling factor |
本文献已被 ScienceDirect 等数据库收录! |
|