Characterization of N-acylation of Go alpha purified from bovine retinas.

Heterogeneous N-terminal acylation has been identified in several retinal proteins localized predominantly in the outer segments of the photoreceptor cells, but it is still unclear whether such a unique heteroacylation is determined by a photoreceptor cell-specific factor or not. Here, we characterized the N-terminal modification of bovine retinal Go alpha, which seems to be involved in the neural activities and is not detected in the photoreceptor outer segments. In the proteolytic fragments of immunoaffinity-purified retinal Go alpha, we found a single N-terminal peptide modified with myristate, and concluded that retinal Go alpha is purely myristoylated, just like brain Go alpha. This result indicates that the heteroacylation has a more restricted origin in the retina, and supports the idea that it is a photoreceptor cell-specific modification.