A novel protein, p19/6.8, specific for cardiac and slow skeletal muscle

Upon in vitro translation of mRNAs from slow (soleus) muscles of the mouse a hitherto undescribed translation product has been detected that was absent from fast sekeletal muscles and was termed p19/6.8 according to its position in 2-dimensional gels. mRNA for p19/6.8 was also found in the ventricle of the heart. p19/6.8 was not detectable by Coomassie blue staining but could be characterised by fractionation of in vivo labelled muscle tissue. It was found to sediment with the particulate fraction at 14 000 × g. The expression of p19/6.8 mRNA appears to be down-regulated in muscles with phasic activity.