Highly Homologous Filamin Polypeptides Have Different Distributions in Avian Slow and Fast Muscle Fibers
The high molecular weight actin-binding protein filamin is located at the periphery of the Z disk in the fast adult chicken pectoral muscle (Gomer, R. H., and E. Lazarides, 1981, Cell, 23: 524-532). In contrast, we have found that in the slow anterior latissimus dorsi (ALD) muscle, filamin was additionally located throughout the l band as judged by immunofluorescence with affinity-purified antibodies on myofibrils and cryosections. The Z line proteins desmin and alpha-actinin, however, had the same distribution in ALD as they do in pectoral muscle. Quantitation of filamin and actin from the two muscle types showed that there was approximately 10 times as much filamin per actin in ALD myofibrils as in pectoral myofibrils. Filamin immunoprecipitated from ALD had an electrophoretic mobility in SDS polyacrylamide gels identical to that of pectoral myofibril filamin and slightly greater than that of chicken gizzard filamin. Two-dimensional peptide maps of filamin immunoprecipitated and labeled with ^(125)I showed that ALD myofibril filamin was virtually identical to pectoral myofibril filamin and was distinct from chicken gizzard filamin.
Additional Information© 1983 Rockefeller University Press. Received for publication 10 January 1983, and in revised form 23 May 1983. We thank Dr. Bruce L. Granger for his helpful comments on the manuscript. This work was supported by grants from the National Institutes of Health, the National Science Foundation, the Muscular Dystrophy Association of America, and a Biomedical Research Support Grant to the Division of Biology, California Institute of Technology. R. H. Gomer was also supported by a predoctoral training grant from the National Institutes of Health. E. Lazarides is a recipient of a Research Career Development Award from the National Institutes of Health.
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