Cardiac alpha-crystallin

Summary A major component of the soluble fraction of rat heart is a homopolymer (M_r about 400–650 k) of a small protein (M_r about 20 k). This cardiac protein, which is highly homologous to alpha-B-crystallin, was isolated in its native state and visualized by electron microscopy. A homogeneous population of globular particles with an average diameter of about 14-16 nM could be seen using either negative staining or rotary shadowing procedures. The structures were globular in nature with a central depression (torus-like structures). Polyclonal antibodies, raised against the cardiac crystallin, were used for the immunocytochemical localization of the macromolecular complexes. Using fluorescent secondary antibodies, a clear and sharp striation of fixed and permeabilized rat heart myocytes could be observed, similar to that observed with anti-desmin antibodies and characteristic for the central region of the I-band. Cardiac crystallin was not found associated with F-actin in preparations of rat heart myofibrils. On the other hand, it was a major contaminant of cardiac desmin preparations. These observations suggest that cardiac crystallin is involved in the organization of cytoskeletal filaments of the Z-lines.Abbreviations SDS Sodium Dodecyl Sulfate - SDS-PAGE SDS-Polyacrylamide Gel Electrophoresis - PMSF Phenyl Methyl Sulfonyl Fluoride - MOPS 3-Morpholino Propanesulfonic Acid - TX-100 Octyl Phenoxy Polyethoxyethanol - CHAPS (3-((3-Cholamidopropyl)Dimethylammonio)-1-Propanesulfonate), - BSA Bovine Serum Albumin - FITC Fluorescein Isothiocyanate - PO Peroxidase