Hydration of retinal and the nature of metarhodopsin II

Allan, Anne E.; Cooper, Alan

doi:10.1016/0014-5793(80)80261-4

Cited by 7 publications

(3 citation statements)

References 11 publications

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“…Alternatively, retinol may interact with water in the bulk phase. In support of this conclusion, essentially the same effect on retinal's C=O band, a downward shift and broadening, was previously observed upon addition of water to all-trans-retinal in acetonitrile (Allan and Cooper, 1980;Pande et al, 1982). The observed broadening of this band upon binding reflects a heterogeneous hydrogen-bonding pattern, resulting in a heterogeneous distribution of carbony1 stretching frequencies.…”

Section: Discussionsupporting

confidence: 74%

The interactions of retinoids with retinol‐binding protein

Manor

Callender

Noy

1993

European Journal of Biochemistry

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We have measured the pre-resonance Raman spectrum of retinal, retinoic acid and retinol in dilute CCl, solutions and when bound to the bovine-serum retinol-binding protein. The comparison reveals that the binding interaction does not involve any specific interactions of the head group and/ or the polyene chain with a particular protein residue. The data indicate hydrogen bonding of bound retinal's head-group oxygen to water, as well as some torsional angle change of its polyene chain upon binding.Retinol (vitamin A alcohol) circulates in blood bound to retinol-binding protein (RBP), a single polypeptide with a molecular mass of 21 kDa that has a single binding site for retinoids (Goodman, 1984). In the circulation, holo-RBP is complexed with another plasma protein, transthyretin. The three-dimensional structure of holo-RBP was determined by X-ray crystallography, and shows that it is composed of a single globular domain comprised of an N-terminal coil, a asheet core, an a-helix, and a C-terminal coil (Cowan et al., 1990;Newcomer et al., 1984). The core of RBP is composed of eight antiparallel p strands which are arranged in two stacked orthogonal p sheets. Retinol is encapsulated within the j? sheets with the p-ionone ring positioned deep within the /? barrel and the isoprene tail extending along the barrel axis to near the surface of the protein.The selectivity of RBP for binding various retinoids and other hydrophobic compounds has been hard to decipher from competition experiments despite intensive efforts. While some groups reported similar affinity of RBP for retinol, citral and p-ionone (Hase et al., 1976), and interpreted the results to indicate lack of a requirement for a fixed polyene chain length, others (Honvitz and Heller, 1974) reported no binding of p-ionone, deducing the opposite conclusion. The isomeric conformation of retinoids was reported to have no effect on binding in some cases (Horwitz and Heller, 1973) and to completely inhibit binding in others (Siegenthaler and Saurat, 1987). Similarly, conflicting reports were published regarding the necessity of a six-membered ring structure as well as a specific requirement of the polar group on the isoprene tail (Goodman and Raz, 1972;Hase et al., 1976; Honvitz and Heller, 1974 recent study of the thermodynamic parameters that contribute to the binding of retinol to RBP have shown that binding is stabilized purely by an increase in entropy and that the enthalpy of binding is approximately zero (Noy and Xu, 1990). These results were interpreted to indicate that binding is mainly stabilized by hydrophobic interactions, and that the hydroxyl moiety of retinol does not play a role in binding to RBP.An ideal method for study of chromophores embedded in proteins is resonance Raman spectroscopy. In this form of vibrational spectroscopy, the spectrum of a molecule is selectively probed by choosing an excitation light which overlaps the electronic absorption band of a chromophore. The resonantly enhanced Raman cross section is hence much larger than that of...

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Section: Discussionsupporting

confidence: 74%

The interactions of retinoids with retinol‐binding protein

Manor

Callender

Noy

1993

European Journal of Biochemistry

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“…Of additional interest as noted before is the notion that a proton may be lost from the putative protonated Schiff base during the critical metarhodopsin I to metarhodopsin II conversion (Cooper & Converse, 1976). A proton is gained from the medium at this time coinciding with a visible spectral shift of spectral change is consistent with a deprotonation of the Schiff base, as is hydrolysis or simple hydration (Allan & Cooper, 1980). These and other experiments suggested that it would be of great interest to prepare and study an opsin molecule with a methyl group attached to its active-site lysine.…”

Section: Discussionmentioning

confidence: 85%

Methylation of the active-site lysine of rhodopsin

Longstaff¹,

Rando²

1985

Biochemistry

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“…The C=N stretch frequency (1657 cm-') indicates that by meta I the Schiff base linking retinal and opsin is still protonated (Doukas et al, 1978). The absence of this band in meta I1 and the good agreement with the fingerprint region of the unprotonated retinylidene Schiff base suggests that the latter moiety is present in meta I1 (Doukas et al, 1978;Pande et al, 1982), but this interpretation has been challenged (Allan and Cooper, 1980;Cooper et al, 1987). On the basis of elegant pH-jump experiments addressing the mechanism of hydrolysis of the retinylidene Schiff base, and of the observation that l 8 0 transfer from H21X0 into retinal may already occur during the meta I to meta I1 transition, Cooper et al (1987) argue that in meta I1 all-trans retinal is either free or bound as a tetrahedral carbanolamine.…”

Section: Photolytic Cascade and Signal Expressionmentioning

confidence: 99%

Recent Chemical Studies Related to Vision

DeGrip

1988

Photochem & Photobiology

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Hydration of retinal and the nature of metarhodopsin II

Cited by 7 publications

References 11 publications

The interactions of retinoids with retinol‐binding protein

The interactions of retinoids with retinol‐binding protein

Methylation of the active-site lysine of rhodopsin

Recent Chemical Studies Related to Vision

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