The Purification, Characterization and Localization of a Parvalbumin‐Like Protein from Chicken‐Leg Muscle

A parvalbumin‐like protein was purified to homogeneity from chicken leg muscle, 40 mg of protein was isolated from 1 kg muscle which is 20% of the amount obtained for parvalbumin isolated from rabbit muscle by a similar procedure. The protein contained 1–2 residues of tyrosine and 1 residue of tryptophan, three arginine residues and a rather small number (4–5) of phenylalanine residues. The differences in the aromatic amino acid content account for the less distinct vibronic structure in the ultraviolet region below 275 nm compared to most other parvalbumins. The protein contained <0.04 residue of γ‐carboxyglutamic acid per molecule. However, the molecular weight of 12000, high content of glutamic acid and aspartic acid, the low content of proline and histidine, and the presence of two calcium atoms per molecule were properties common to parvalbumins. Immunprecipitation experiments in agar using anti‐chicken parvalbumin‐like protein indicated that an immunologically indistinguishable form of this protein is present in heart, white and red back muscles, breast, stomach, brain, pancreas, small intestine and kidney, but not in spleen, liver and blood. The distribution is therefore as ubiquitous as G‐actin or β‐actinin. Parvalbumin‐like protein was found to accumulate in differentiating primary muscle cell cultures after 120 h. This approximates to the time on which myosin and actin start to accumulate, proteins necessary for myofibril assembly. Experiments to investigate the localization of parvalbumin‐like protein, using the indirect immunofluorescence technique showed regular cross‐striation patterns within the I band of isolated myofibrils. The results suggest that parvalbumin‐like protein may interact with one or more of the protein components of the thin filament thus being involved in the contractile process. This component could be β‐actinin which copurified with parvalbumin‐like protein through the DEAE‐cellulose step (see following paper).