Calcium-binding protein, parvalbumin, is reduced in mutant mammalian muscle with abnormal contractile properties.

To elucidate the biochemical basis of hereditary muscle diseases in an experimental mammal, we performed polypeptide analyses on skeletal muscles of neuromuscular mutants of the mouse. In one of these, "arrested development of righting response" (adr), the concentration of the soluble Ca2+-binding protein parvalbumin was drastically reduced in comparison to wild type. This reduction was not an unspecific consequence of muscle disease, as it was not observed in two other neuromuscular mouse mutants, "wobbler" (wr) and "motor endplate disease" (med or medjo). Isometric twitches of adr muscle had only slightly prolonged contraction and half-relaxation times, yet long-lasting after-contractions were observed upon repeated (20-100 Hz) direct stimulation. Thus, parvalbumin may be mainly involved in the relaxation after tetanic contraction of fast-twitch fibers.