(Ca2+ + Mg2+)‐dependent ATPase mRNA from smooth muscle sarcoplasmic reticulum differs from that in cardiac and fast skeletal muscles

Abstract

We have investigated some characteristics of the sarcoplasmic reticulum (Ca²⁺ + Mg²⁺)-dependent ATPase (Ca²⁺-ATPase) mRNA from smooth muscle using specific cDNA probes isolated from a rat heart cDNA library. RNA blot analysis has shown that the Ca²⁺-ATPase mRNA expressed in smooth muscle is identical in size to the cardiac mRNA but differs from that of fast skeletal muscle. S₁ nuclease mapping has moreover shown that the cardiac and smooth muscle isoforms possess different 3′-end sequences. These results indicate that a distinct sarcoplasmic reticulum Ca²⁺-ATPase mRNA is present in smooth muscle.