title: Histidine tagging both allows convenient single-step purification of bovine rhodopsin and exerts ionic strength-dependent effects on its photochemistry.
abstract: For rapid single-step purification of recombinant rhodopsin, a baculovirus expression vector was constructed containing the bovine opsin coding sequence extended at the 3'-end by a short sequence encoding six histidine residues. Recombinant baculovirus-infected Spodoptera frugiperda cells produce bovine opsin carrying a C-terminal histidine tag (v-opshis6x). The presence of this tag was confirmed by immunoblot analysis. Incubation with 11-cis-retinal produced a photosensitive pigment (v-Rhohis6x) at a level of 15-20 pmol/10(6) cells. The histidine tag was exploited to purify v-Rhohis6x via immobilized metal affinity chromatography. Optimized immobilized metal affinity chromatography yielded a binding capacity of > or = 35 nmol of v-Rhohis6x per ml of resin and purification factors up to 500. Best samples were at least 85% pure, with an average purity of 70% (A280 nm/A500 nm = 2.5 +/- 0.4, n = 7). Remaining contamination was largely removed upon reconstitution into lipids, yielding rhodopsin proteoliposomes with a purity over 95%. Spectral analysis of v-Rhohis6x showed a small but significant red shift (501 +/- 1 nm) compared to wild type rhodopsin (498 +/- 1 nm). The pK alpha of the Meta I<==>Meta II equilibrium in v-Rhohis6x is down-shifted from 7.3 to 6.4 resulting in a significant shift at pH 6.5 toward the Meta I photointermediate. Both effects are reversed upon increasing the ionic strength. FT-IR analysis of the Rho-->Meta II transition shows that the corresponding structural changes are identical in wild type and v-Rhohis6x.
authors.affiliation: Department of Biochemistry, University of Nijmegen, The Netherlands.
authors.forename: J J
authors.initials: JJ
authors.lastname: Janssen
authors.forename: P H
authors.initials: PH
authors.lastname: Bovee-Geurts
authors.forename: M
authors.initials: M
authors.lastname: Merkx
authors.forename: W J
authors.initials: WJ
authors.lastname: DeGrip
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002460:Cell Line; D002846:Chromatography, Affinity / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D006639:Histidine; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009994:Osmolar Concentration; D010777:Photochemistry; D010782:Photolysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D012160:Retina / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D017299:Rod Opsins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016324:Sequence Tagged Sites; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D018411:Spodoptera; D014162:Transfection
chemical_list: D011994:Recombinant Proteins; D017299:Rod Opsins; D006639:Histidine; D012243:Rhodopsin