Protein configuration changes in the photolysis of rhodopsin II. The sequence of intermediates in thermal decay of cattle metarhodopsin in vitro
Affiliation:
1. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China;2. Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People’s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200011, China;3. R&D Center, Lifetech Scientific (Shenzhen) Co Ltd, Shenzhen 518057, China;4. Department of Interventional Radiology and Vascular Surgery, Peking University Third Hospital, Beijing 100191, China;5. Department of Biomedical Engineering, College of Engineering, University of North Texas, Denton, TX 76207, USA;6. International Research Organization for Advanced Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-Ku, Kumamoto 860-8555, Japan;1. Dipartimento di Scienze Chimiche, Della Vita e della Sostenibilità Ambientale and Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici, Università di Parma, Parco Area Delle Scienze 11/A, 43124, Parma, Italy;2. Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131, Padova, Italy;1. Western University, Department of Psychology, London, ON, Canada;2. Colorado College, Department of Psychology, Colorado, CO, USA;1. Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, IL 60208, United States;2. Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, United States;3. Department of Chemistry, University of Wisconsin-Stevens Point, 2100 Main Street, Stevens Point, WI 54481, United States;4. Department of Chemistry, Memorial University of Newfoundland, 230 Elizabeth Avenue, St. John’s, Newfoundland and Labrador, A1C 5S7, Canada;5. Department of Chemistry and Biochemistry and Centre for NanoScience Research, Concordia University, 7141 Sherbrooke St. W., Montréal, Québec, H4B 1R6, Canada;6. Department of Chemistry and Biochemistry, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA 90032, United States;1. Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763, Republic of Korea;2. Analysis and Evaluation Department, Egyptian Petroleum Research Institute (EPRI), Nasr City 11727, Cairo, Egypt;3. Department of Biotechnology, University Institute of Engineering Technology (UIET), Panjab University, Chandigarh, India;4. Department of Nanomaterials and Application Technology, Center of Innovative and Applied Bioprocessing, Sector 81 (Knowledge City), S.A.S. Nagar 140306, Punjab, India;5. Central Scientific Instruments Organization (CSIR-CSIO), Sector 30 C, Chandigarh 160030, India;1. Center for Drug Delivery Systems, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Institut de Sciences Moléculaires D''Orsay, Université Paris-Saclay, Orsay Cedex 91400, France;4. Key Laboratory of Modern Chinese Medicine Preparations, Ministry of Education, Jiangxi University of Traditional Chinese Medicine, Nanchang 330004, China;5. School of Pharmaceutical Sciences, Anhui University of Chinese Medicine, Hefei 230012, China;6. NMPA Key Laboratory for Quality Research and Evaluation of Pharmaceutical Excipients, National Institutes for Food and Drug Control, Beijing 100050, China
Abstract:
On illumination of solutions of the visual chromoprotein, cattle rhodopsin, there is a sequence of thermal, first-order reactions. Whereas previous work has shown the first two appear to involve a rearrangement of the protein structure in which the solvent plays only a secondary role, the thermal changes beginning with metarhodopsin and terminating with a hydrolysis yielding the protein, opsin and trans-retinal all involve the solvent directly. Our studies show that there are five intermediates in the solvent-dependent sequence (subscripts denote spectral maxima): Previous flash-photolysis studies1 and the present kinetic data are consistent with the notion of three forms of metarhodopsin478 decaying by first-order, pH-dependent processes to metarhodopsin380. This is also borne out by the behavior of the metarhodopsin478 ↔ metarhodopsin380 reaction at different temperatures and pH's. The decay of metarhopopsin380 to metarhodopsin465 has a small temperature coefficient, a large negative ΔS∗ role=presentation style=font-size: 90%; display: inline-block; position: relative;>, and is slow enough to be rate controlling at physiological temperatures. Metarhodopsin465 (transient orange) decays to N-retinylideneopsin (indicator yellow) by a single first-order process and like metarhodopsin478 → metarhodopsin380 has a large positive ΔH∗ role=presentation style=font-size: 90%; display: inline-block; position: relative;> and ΔS∗ role=presentation style=font-size: 90%; display: inline-block; position: relative;> rate constant is about io6 times smaller. Irradiation of metarhodopsin465 yields rhodopsin498, isorhodopsin487 and cis-isomers of retinal. The hydrolysis of N-retinylidene-opsin to retinal and opsin is faster than the metarhodopsin465 → N-retinylidene-opsin process at pH 7 but is sufficiently slower and lower and higher pH's to be observed.
