Muscle beta-actinin and serum albumin of the chicken are indistinguishable by physicochemical and immunological criteria.

Abstract

Chicken muscle ,B-actinin is considered to be one ofthe "true" myofibrillar components due to its specific binding to isolated myofibrils. Surprisingly, the direct comparison of this muscle protein with serum albumin, both isolated from chicken, showed that they behaved identically under several electrophoretic conditions. Furthermore, immunoreplica gels and doubleimmunodiffusion tests with antibodies prepared against 3-actinin established the serological identity of both proteins. No significant differences were found by circular dichroic spectroscopy or in amino acid composition. In addition, the amino-terminal sequences of both proteins were identical (H2N-Asp-Ala-Glu-HisLys-Ser-Glu-Ile-Ala-His-Arg-Tyr-Asn-Asp-Leu-). Combined, these results strongly indicate that, muscle ,B-actinin and serum albumin are similar, if not identical.There is a class ofminor myofibrillar components called actinins which were originally thought to be structurally related to actin (1, 2). Later, however, it became apparent that the physicochemical properties of the purified proteins were clearly different from those ofactin. Nevertheless, the name "actinin" has been retained because these proteins appear to interact directly with actin itself. At present, three different actinins, a, 13, and y, have been described (3-9).Among these, the status of,-actinin is the least clear, and two (ifnot three) proteins are currently designated as such. Two monomeric and possibly homologous proteins with molecular weights of60,000 and 65,000 have been isolated from rabbit and chicken muscle, respectively (10, 11). A third, dimeric protein (subunit molecular weights of 37,000 and 34,000), also designated ,3-actinin, was subsequently described by Maruyama et al. (12). Its relationship to the monomeric /3-actinin(s) is not understood and will therefore not be considered.Localization of the monomeric form(s) from both rabbit and chicken by indirect immunofluorescence revealed a strong and specific binding to the I region of isolated myofibrils (10, 11) and suggested involvement in the myofibrillar structure. Ultrastructural analysis more precisely demonstrated that the chicken protein was specifically oriented in two parallel stripes running transversely across the muscle fiber at the end of the thick filament-i.e., at the A/I junction (unpublished observation).In this work we present some unexpected results that indicate similarity (ifnot identity) ofthe structural muscle ,3-actinin with serum albumin. Both components, isolated from chicken, were found to be indistinguishable by electrophoresis in the presence or absence of NaDodSO4; their spectral properties, amino-terminal sequences, and immunological properties were also the same. MATERIALS AND METHODSProteins. Rabbit skeletal muscle actin, chicken ,3-actinin, and rabbit antibodies against chicken 13-actinin were prepared as described (11,(13)(14)(15) Amino-Terminal Sequences. The amino acid sequences were automatically determined with a Beckman sequencer model 890B (updated), with 4-N,N...

Sciatin Is a Transferrin‐Like Polypeptide

“…In this regard, preliminary studies in this laboratory using pulse labeling with [3H]amino acids followed by immunoprecipitation with antisciatin IgG have demonstrated that mixed neuronal-glial cultures synthesize sciatin and that this synthesis is abolished by puromycin (Markelonis, Oh, Sofia, and Kim, unpublished data). Therefore, the relationship between sciatin and serum transferrin may be similar to that observed between avian muscle p-actinin and serum albumin, which were shown to be identical molecules by structural and immunological criteria (Heizmann et al, 1981). However, since monoclonal antibodies that do not cross-react with sciatin have been elicited against the serum factor (Oh, Cha, and Markelonis, unpublished data), these two proteins, although structurally very similar, may ultimately prove to be quite distinct.…”

Culinary Biophysics: on the Nature of the 6X°C Egg

“…14,15 The peak denaturation temperature of BSA using differential scanning calorimetry (DSC) is found at ∼60°C depending on the conditions used, 16 although the secondary structure starts to be lost permanently above 50°C. 17 The good gelation ability of BSA has long been established, 18 and it is known to form gels at <60°C.…”

Further characterization of the N-terminal copper(II)- and nickel(II)-binding motif of proteins. Studies of metal binding to chicken serum albumin and the native sequence peptide

“…Chicken serum albumin (CSA) differs from both HSA and DSA in that it has glutamic acid at the third position [12]. This is due to an insertion in the protein sequence when compared with HSA, as opposed to the substitution observed in DSA.…”