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The primary structure of myoglobin of the seal of Lake Baikal (East Siberia) Phoca siberica, determined by sequencing the whole protein and peptides obtained by the cyanogen bromide or proteinase cleavage and separated by the microcolumn liquid chromatography, was found to be identical to the primary structures of myoglobins of the harbour seal Phoca vitulina largha and the grey seal Halehoerus gryphus. It suggests that these species separated from a common ancestor less than seven million years ago.

Apomembranes prepared from the photoreceptor disks were subjected to chymotryptic hydrolysis. The insoluble material, containing the membrane-bound peptides was removed by centrifugation, and the water-soluble peptides of the supernatant were separated by ion-exchange chromatography on AG 50W X 4 followed by high performance liquid chromatography. The insoluble peptides were separated by gel-filtration on Bio-Gel P-30 in 80% formic acid. Amino acid sequence of peptides containing in total 296 amino acid residues and comprising 85% of the rhodopsin polypeptide chain was determined.

The alpha- and beta-subunits of the GTP-binding protein (transducin) from cattle retina were cleaved with cyanogen bromide. 21 peptides covering 90-100% of the amino acid sequence of the alpha- and beta-subunits were isolated from the hydrolyzate. Cyanogen bromide peptides complete or partial amino acid sequence was determined, the results were compared with those by Numa and coworkers [1] and Lochrie et al. [2] at the primary structure of the transducin alpha-subunit deduced from the nucleotide sequence of the cDNA. The structure by Lochrie is shown to differ much from the true structure of the alpha-subunit; probably, the investigators isolated cDNA, corresponding to the gene for some GTP-binding protein homologous to transducin, but not to the gene for the transducin alpha-subunit. The Numa's structure also contains an error. The final primary structure of the transducin alpha-subunit is given. The protein polypeptide chain consists of 349 amino acid residues and has an acetylmethionine residue as the N-terminal residue.

Gel electrophoresis in the presence of sodium dodecyl sulphate followed by electroblotting was employed in sample preparation for microsequencing proteins and protein fragments. Three types of solid supports were compared: glass fiber filters modified by aminopropyltriethoxysilane or covered with polybrene, and polyvinylidenedifluoride membranes. N-Terminal amino acid sequences of several proteins (Mr 14-140 kDA were determined on a gas-phase sequencer with the standard programme; 20-200 pmoles of the protein can be assayed by this method.