CONFORMATIONAL CHANGE DUE TO REDUCTION OF CYTOCHROME-C-OXIDASE IN LAURYL MALTOSIDE - PICOSECOND TIME-RESOLVED TRYPTOPHAN FLUORESCENCE STUDIES ON THE NATIVE AND HEAT MODIFIED ENZYME

被引:15
作者
DAS, TK [1 ]
MAZUMDAR, S [1 ]
机构
[1] TATA INST FUNDAMENTAL RES, CHEM PHYS GRP, BOMBAY 400005, MAHARASHTRA, INDIA
来源
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY | 1994年 / 1209卷 / 02期
关键词
CYTOCHROME-C OXIDASE; TIME-RESOLVED FLUORESCENCE; PROTEIN CONFORMATION; TRYPTOPHAN; (BOVINE HEART);
D O I
10.1016/0167-4838(94)90189-9
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Detailed fluorescence studies on bovine heart cytochrome-e oxidase (CcO) has been carried out in lauryl maltoside solution. Steady-state fluorescence of the tryptophan residues of the enzyme showed that the fluorophores are embedded deep inside the hydrophobic protein cavity. Time resolved studies of tryptophan fluorescence of native and heat treated CcO have been carried out in both reduced and oxidised forms using synchronously pumped pulsed picosecond dye laser and single photon counting technique. Decay of the tryptophan fluorescence have been fitted using discrete four exponential model. Amplitude distribution of lifetimes also showed four distinct regions in the analysis of the decay profiles by maximum entropy method (MEM). The results indicate that controlled heat treatment of CcO affects the conformation of the enzyme near the active centers which makes it incapable of active proton pumping while the electron transfer property is still conserved. Reduction of the native CcO is associated with a large conformation change in lauryl maltoside near the active centers which is not observed in case of CcO encapsulated in vesicles. Reduction of the heat treated enzyme was found to have a conformation different from the reduced native CcO.
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页码:227 / 237
页数:11
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