Dr. BARBARA GOLDEN

The focus of our research is the structure and folding of functional RNAs. Unlike proteins, RNAs have a highly charged backbone, only 4 different monomeric units (compared to the 20 amino acids that make up proteins) and functional groups that are largely sequestered within the major and minor grooves of the double helix. Yet, in the presence of magnesium ion, many RNA molecules have stable, globular, tertiary structures that support biological catalysis. To understand how these molecules fold and function, we are investigating the structure and function of these RNA molecules using biochemistry, molecular biology and X-ray crystallography.

Group I introns catalyze transesterification reactions by activating a guanosine nucleophile for attack on the phosphodiester backbone. The structure of a ribozyme derived from a self-splicing intron from bacteriophage Twort was recent solved at 3.6 Å resolution. The structure reveals extensive interactions between three domains that construct an active site composed of RNA, and a complex binding pocket for the guanosine nucleotide substrate.

We are also studying an encapsidation signal from Sindbis virus, a member of the alphavirus genus. Initiation of nucleocapsid core assembly begins with recognition of an encapsidation signal within the viral RNA by capsid protein. Surprisingly, the encapsidation signal of Sindbis virus appears to fold into a compact structure upon interaction with two molecules of capsid protein. These data support a model in which dimerization of capsid protein is promoted by folding of the encapsidation signal and thus the structure of the RNA may play a significant role in intiation of nucleocapsid assembly.