UNC45B and congenital myopathy: Among the proteins showing this pattern, one finds several other proteins not previously analyzed with respect to fiber type, including PRKAR1A (cAMP-dependent protein kinase regulatory subunit 1α), a component of protein kinase A (PKA), the kinase mediating the effect of β-adrenergic stimulation in muscle cells, and UNC45B, a myosin chaperone whose mutation causes a congenital myopathy [40, 41].