Solid-state sup 13 C NMR of the retinal chromophore in photointermediates of bacteriorhodopsin: Characterization of two forms of M

Journal Article · Mon Jan 09 23:00:00 EST 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00427a033· OSTI ID:5481198

Smith, S O; Courtin, J; van den Berg, E; Winkel, C; Lugtenburg, J; Herzfeld, J; Griffin, R G ^[1]

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1. Massachusetts Institute of Technology, Cambridge (USA)

Solid-state {sup 13}C NMR spectra of the M photocycle intermediate of bacteriorhodopsin (bR) have been obtained from purple membrane regenerated with retinal specifically {sup 13}C labeled at positions 5, 12, 13, 14, and 15. The M intermediate was trapped at {minus}40{degree}C and pH = 9.5-10.0 in either 100 mM NaCl (M (NaCl)) or 500 mM guanidine hydrochloride (M (Gdn-HCl)). The {sup 13}C-12 chemical shift at 125.8 ppm in M (NaCl) and 128.1 ppm in M (Gdn-HCl) indicates that the C{sub 13}{double bond}C{sub 14} double bond has a cis configuration, while the {sup 13}C-13 chemical shift at 146.7 ppm in M (NaCl) and 14.57 ppm in M (Gdn-HCl) demonstrates that the Schiff base in unprotonated. The principal values of the chemical shift tensor of the {sup 13}C-5 resonance in both M (NaCl) and M (Gdn-HCl) are consistent with a 6-s-trans structure and a negative protein charge localized near C-5 as was observed in dark adapted bR. The {approximately}5 ppm upfield shift of the {sup 13}C-5 M resonance relative to {sup 13}C-5 bR{sub 568} and bR{sub 548} is attributed to an unprotonated Schiff base in the M chromophore. Of particular interest in this study were the results obtained from {sup 13}C-14 M. In M (NaCl), a dramatic upfield shift was observed for the {sup 13}C-14 resonance relative to unprotonanted Schiff base model compounds. In contrast, in M (Gdn-HCl) the {sup 13}C-14 resonance was observed at 125.7 ppm. The different {sup 13}C-14 chemical shifts in these two M preparations may be explained by different C{double prime}N configurations of the retinal-lysine Schiff base linkage, namely, syn in NaCl and anti in guanidine hydrochloride.

• OSTI ID: 5481198
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:1; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
CARBON 13
CARBON ISOTOPES
CHEMICAL BONDS
CHEMICAL SHIFT
EVEN-ODD NUCLEI
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEMBRANES
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
RESONANCE
RHODOPSIN
SPECTRA
STABLE ISOTOPES
VITAMIN A
VITAMINS