A domain of the α-subunit of rabbit phosphorylase kinase shows homologies with regions of rabbit α-tropomyosin, human EGF receptor, and the α chain of bovine S-100 protein Available to Purchase

Sequence comparison of the α-subunit of phosphorylase kinase with α-tropomyosin revealed 32% identity, and 49% similarity, between the region of α-tropomyosin coded by exon 5 and a 39 amino acid segment of the kinase subunit. A subsequence of the α-subunit segment and a sequence overlapping the same α-subunit region are homologous with: (a) a region of the cytoplasmic domain of EGF receptor (50% identity) and (b) a Ca²⁺-binding domain of the α chain of S-100 protei (50% identity) respectively. Statistical analysis shows that these homologies are significant. The biological implication of the above similarities is discussed.