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State-dependent disulfide cross-linking in rhodopsin.
H Yu1, M Kono, D D Oprian
1Department of Biochemistry, Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA.
Biochemistry
|October 3, 1999
Summary
This study reveals new tertiary interaction sites in rhodopsin using disulfide cross-linking. Photoexcitation alters cysteine cross-linking patterns, indicating conformational changes in this important visual pigment.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Rhodopsin tertiary interactions are crucial for its function.
- Split receptor and disulfide cross-linking methods offer insights into protein structure.
- Previous work established a novel detection technique for tertiary interactions.
Purpose of the Study:
- To investigate cross-linking reactions between native cysteines in rhodopsin.
- To compare cross-linking in the ground state versus photoexcited states.
- To elucidate conformational changes upon rhodopsin photoexcitation.
Main Methods:
- Utilized a split receptor and disulfide cross-linking approach.
- Engineered cysteines into separate opsin fragments.
- Detected disulfide cross-links via electrophoretic mobility shift after Cu(phen)3(2+) treatment.
Main Results:
- In the dark, Cys140 (TM3) cross-links with Cys222 (TM5).
- Upon photoexcitation, Cys140 also cross-links with Cys316.
- The rate of Cys140-Cys222 cross-linking increases significantly after photobleaching.
Conclusions:
- The study identifies specific cysteine residues involved in rhodopsin tertiary interactions.
- Photoexcitation induces significant conformational changes in rhodopsin.
- The developed cross-linking method is effective for studying dynamic protein structures.