11-cw retinaldehyde

We have determined molar-extinction coefficients for human rCRALBP with bound 11-cw-retinaldehyde (e " = 43,400 Af" cm and = 13,400 M" cm ) and with bound 9-cw-retinaldehyde [e sonm 44 goo A/" cm and e " = 20,700 A/ cm ] Similar molar-extinction coefficients have been determined for bovine CRALBP with bound 11-cw-retinaldehyde (28). 

A typical HPLC profile for the retinoid present in bovine RPE cytosol is shown in Fig. 6. After the initial breakthrough region at 8 min, only two major peaks are present. They correspond to 11-cw-retinaldehyde (peak 1) and all-rrani-retinol (peak 6). Therefore, most of the retinaldehyde in the cytosol is 11-cis, while nearly all of the retinol is all-trans. This has been found to be generally true for bovine and human RPE cytosols. 

Of particular interest is the fact that 11-c/s-ietinoid in bovine retina cytosol consists of 11-cis-retinol as well as 11-cw retinaldehyde. In contrast, only 11-c/s-retinaldehyde is present in the RPE cytosol [Saari (1982) Saari et al. (1982) see also Liou et al. (1982c)]. Since bovine and other mammalian retinas cannot utilize 1 l-cu-retinol for rhodopsin regeneration (see Section III,G,3), its... 

Retinaldehyde, especially ll-cw-retinaldehyde, plays a special role in the visual process the 11-cis isomer binds to the protein opsin to form the visual protein rhodopsin. This derivative has been studied intensely through the use of deuterium-labeled retinaldehyde. 

Retinoids 11-ci.y-retinaldehyde can be obtained through the National Eye Institute, Fundamental Retinal Processes Research Program, National Institute of Health, Bethesda, MD. 9-cw-retinaldehyde is obtainable from Sigma Chemical Company Both retinoids are stored dry, under argon at -70°C m the dark, and dissolved in ethanol for labeling purposes. 

Fig 5. Spectral Analysis of rCRALBP Before and After Bleaching Fusion and nonfusion rCRALBP with bound 11 -cw-retmaldehyde exhibit absorption maximum at 425 nm before bleaching. The proteins undergo a spectral shift to about 380 nm upon exposure to bleaching illumination, owing to the production of free, unbound att-trans-retinaldehyde. 

Both 11-ci -retinaldehyde and 11-cw-retinol have been recovered from purified rCRALBP after labeling of the crude-bacterial lysate with only 11-cts-retinaldehyde This indicates that retinoid modification can occur during the labeling and/or protem-punfication steps. 

Are the various isomers mobilized and transported in different ways in the RPE This appears to be the case. The retinyl esters stored in the RPE contain 11-cis as well as all-trans isomers. As discussed in Section III,D, 11-cw- and all-franj-retinoids are streamed separately in the RPE cytosol, the 11-cis isomer as retinaldehyde and the all-trans isomer as retinol, each bound to its own, separate transport protein. Whether both retinoids are transported through... 

All-tra/w-retinol, 11-cw-retinol (A2) and 11-m-retinaldehyde are found in the 1PM (Liou et al., 1982c). At present, it is not clear which retinoid, or which isomer, is in transit from the RPE to the ROS. With regard to carrier proteins, the evidence suggests that CRBP and CRAIBP are present in the 1PM (Liou et al., 1982c), but it is probable that they have leached from the RPE and retina cytosols where both proteins occur. On the other hand, interstitial retinol-binding protein is believed to be a true IPM protein because it is absent from the RPE and retina cytosols. This conclusion has been confirmed by immunocytochemical observations in the author s laboratory (Fong et al., 1984) and by Bunt-Milam and Saari (1983). Although IRBP binds the all-tranj-retinol that is released when rhodop-sin is bleached, it also carries some 11-cis isomer, and it has not been established whether it may be implicated in the two-way transport of retinoids. 

Fig. 13. Regeneration of rhodopsin in suspensions of frog ROS membranes. Enzyme and opsin source bleached ROS membranes in Ringer s (i mi), pH 7.4, temperature 25°. Additives were as foiiows 11-cw-retinol, 100 nmol 11-cu-retinaldehyde, 50 nmol NAD+ ( ) or NADP" (X), 200 nmol. Retinoids were added in about 10 p.1 ethanol. (From Bridges, 1976b.)...

Retinoids. The 9,11-di-cw-isomer of retinaldehyde (90) has been prepared in six steps from the C15 aldehyde (93) and used to form a 9,11-di-m-rhodopsin with cattle opsin.60 The 9,1 l-di-cw-isomer was also one of four di-cis forms obtained by irradiation of all-fra/w-retinaldehyde in acetonitrile.61 The sterically hindered... 

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