Water and Peptide Backbone Structure in the Active Center of Bovine Rhodopsin

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• 作者：Tomoko Nagata ; Akihisa Terakita ; Hideki Kandori ; Daisuke Kojima ; Yoshinori Shichida ; and Akio Maeda
• 刊名：Biochemistry
• 出版年：1997
• 出版时间：May 20, 1997
• 年：1997
• 卷：36
• 期：20
• 页码：6164 - 6170
• 全文大小：151K
• 年卷期：v.36,no.20(May 20, 1997)
• ISSN：1520-4995

文摘

Difference FTIR spectra in the conversion of rhodopsin orisorhodopsin to bathorhodopsinwere recorded for recombinant wild-type and E113Q bovine rhodopsins.Differences in various vibrationalmodes between E113Q and the wild-type proteins whose Schiff basesinteract with chloride and Glu113,respectively, were analyzed. Water molecules in rhodopsin thatchange upon formation of bathorhodopsinare detected by a change in frequency of the O-H stretching vibrationfrom 3538 to 3525 cm^-1.Thischange in the wild-type protein is absent in E113Q. One or a fewwater molecules are therefore suggestedto be located in the proximity of Glu113, the counterion of the Schiffbase. Another water vibration at3564 cm^-1, which is shifted to 3542cm^-1 in bathorhodopsin in the wild type,persists in E113Q but with~5-cm^-1 shift toward higher frequency.This is due to water molecules that may be located at asitesomewhat more remote from Glu113. Structural changes of somepeptide carbonyls and amides are alsoabsent in E113Q. On the other hand, the E113Q protein shows shiftsof the N-H⁺ stretching vibrationalband, that is probably due to the protonated Schiff base, uponconversion of rhodopsin to bathorhodopsin.No corresponding changes were observed in the wild type. Wepropose a model in which a water moleculeinteracts with Glu113, the protonated Schiff base, and peptidecarbonyls, and amides. These residuesundergo structural changes upon formation ofbathorhodopsin.