Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Ga proteins.

Proceedings of the National Academy of Sciences of the United States of America

PubMedID: 22529365

Jones JC, Jones AM, Temple BR, Dohlman HG. Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Ga proteins. Proc Natl Acad Sci USA. 2012;109(19):7275-9.
Proteins with similar crystal structures can have dissimilar rates of substrate binding and catalysis. Here we used molecular dynamics simulations and biochemical analysis to determine the role of intradomain and interdomain motions in conferring distinct activation rates to two Ga proteins, Ga(i1) and GPA1. Despite high structural similarity, GPA1 can activate itself without a receptor, whereas Ga(i1) cannot. We found that motions in these proteins vary greatly in type and frequency. Whereas motion is greatest in the Ras domain of Ga(i1), it is greatest in helices aA and aB from the helical domain of GPA1. Using protein chimeras, we show that helix aA from GPA1 is sufficient to confer rapid activation to Ga(i1). Ga(i1) has less intradomain motion than GPA1 and instead displays interdomain displacement resembling that observed in a receptor-heterotrimer crystal complex. Thus, structurally similar proteins can have distinct atomic motions that confer distinct activation mechanisms.