부산대학교 도서관

PURPOSE. Interphotoreceptor retinoid-binding protein(IRBP), an extracellular protein believed to support the exchange of retinoidsbetween the neural retina and retinal pigment epithelium (RPE) in the vertebrateeye, exhibits a modular, i.e., repeat, structure. The present study was undertakento determine whether an individual module of IRBP has activity in retinoidtransfer between the RPE and rod photoreceptors. METHODS. The retinoid transfer activity of a recombinant protein correspondingto the fourth module of Xenopus laevis IRBP (X4IRBP) was examinedin two ways. First, X4IRBP was tested for its ability to support the regenerationof porphyropsin in detached/reattached Xenopus retina/RPE-eyecups.Following illumination and removal of native IRBP, Xenopus eyecupssupplemented with 42 μM X4IRBP or (as a control) Ringer's solution wereincubated in darkness and then analyzed for regenerated porphyropsin. Second,toad ( Bufo marinus ) RPE-eyecup preparations were used to evaluateX4IRBP's ability to promote the release of 11-cis retinal from the RPE. RESULTS. The regeneration of porphyropsin in X4IRBP-supplemented Xenopus retina/RPE-eyecups (0.45 ± 0.04 nmol; mean ± SEM, n =11) exceeded that in controls (0.13 ± 0.02 nmol, n = 11). For promotingthe release of 11-cis retinal from the toad RPE, 42 μM X4IRBP was moreeffective than equimolar bovine serum albumin although considerably less thanthat of 26 μM native bovine IRBP. CONCLUSIONS. The results indicate a low but significant activity of IRBP'sfourth module in reactions relevant to retinoid exchange. [ABSTRACT FROM AUTHOR]