Biomaterial Database

On the disulphide bonds of rhodopsins. 1987

S Al-Saleh, and M Gore, and M Akhtar

Department of Biochemistry, University of Southampton, U.K.

Carboxymethylation using 14C- or 3H-labelled iodoacetic acid has been used to identify the cysteine residues in bovine rhodopsin involved in the formation of the two intramolecular disulphide bridges. Iodo[2-14C]acetic acid was used to modify 5.8-5.9 residues of cysteine under non-reducing conditions. After dialysis and reduction of disulphide bridges by 2-mercaptoethanol, iodo[2-3H]acetic acid was employed to covalently modify 3.3-3.6 residues of cysteine. Peptide purification and sequencing has unambiguously shown that cysteine residues 322 and 323 are only carboxymethylated after reduction of disulphide bridges. Indirect evidence presented, now coupled with the earlier finding [Findlay & Pappin (1986) Biochem. J. 238, 625-642] suggests that the other disulphide bridge is formed between cysteine residues 110 and 187. A comparison is made of all the sequences of mammalian rhodopsins and colour pigments and attention is drawn to the fact that whereas Cys-322 and Cys-323 are conserved only in three rhodopsins (bovine, ovine and human), the residues corresponding to Cys-110 and Cys-187 are found in all the visual proteins (from rods as well as human cones).

UI	MeSH Term	Description	Entries
D007461	Iodoacetates	Iodinated derivatives of acetic acid. Iodoacetates are commonly used as alkylating sulfhydryl reagents and enzyme inhibitors in biochemical research.	Iodoacetic Acids,Acids, Iodoacetic
D008745	Methylation	Addition of methyl groups. In histo-chemistry methylation is used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid. (From Stedman, 25th ed)	Methylations
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D004220	Disulfides	Chemical groups containing the covalent disulfide bonds -S-S-. The sulfur atoms can be bound to inorganic or organic moieties.	Disulfide
D004590	Electrophoresis, Paper	Electrophoresis in which paper is used as the diffusion medium. This technique is confined almost entirely to separations of small molecules such as amino acids, peptides, and nucleotides, and relatively high voltages are nearly always used.	Paper Electrophoresis
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012168	Retinal Pigments	Photosensitive protein complexes of varied light absorption properties which are expressed in the PHOTORECEPTOR CELLS. They are OPSINS conjugated with VITAMIN A-based chromophores. Chromophores capture photons of light, leading to the activation of opsins and a biochemical cascade that ultimately excites the photoreceptor cells.	Retinal Photoreceptor Pigment,Retinal Pigment,Visual Pigment,Visual Pigments,Retinal Photoreceptor Pigments,Photoreceptor Pigment, Retinal,Photoreceptor Pigments, Retinal,Pigment, Retinal,Pigment, Retinal Photoreceptor,Pigment, Visual,Pigments, Retinal,Pigments, Retinal Photoreceptor,Pigments, Visual
D012243	Rhodopsin	A purplish-red, light-sensitive pigment found in RETINAL ROD CELLS of most vertebrates. It is a complex consisting of a molecule of ROD OPSIN and a molecule of 11-cis retinal (RETINALDEHYDE). Rhodopsin exhibits peak absorption wavelength at about 500 nm.	Visual Purple
D019807	Iodoacetic Acid	A derivative of ACETIC ACID that contains one IODINE atom attached to its methyl group.	Monosodium Iodoacetate,Monoiodoacetic Acid,Sodium Iodoacetate,Acid, Iodoacetic,Acid, Monoiodoacetic,Iodoacetate, Monosodium,Iodoacetate, Sodium