these effects may be mediated by cyclic amp-stimulated phosphorylation of specific proteins located in the sarcolemma , sarcoplasmic reticulum , and myofilaments via one or more protein kinases , although experimental verfication of the possible relationship between protein phosphorylation and altered ca2+ binding properties at specific sites in the membranes is at present largely lacking .
C0033640
protein kinases
C1158886
protein