The Structural Basis for Cdc42-Induced Dimerization of IQGAPs.

In signaling, Rho-family GTPases bind effector proteins and alter their behavior. Here we present the crystal structure of Cdc42·GTP bound to the GTPase-activating protein (GAP)-related domain (GRD) of IQGAP2. Four molecules of Cdc42 are bound to two GRD molecules, which bind each other in a parallel dimer.

Linking aptamer-ligand binding and expression platform folding in riboswitches: prospects for mechanistic modeling and design.

The power of riboswitches in regulation of bacterial metabolism derives from coupling of two characteristics: recognition and folding. Riboswitches contain aptamers, which function as biosensors. Upon detection of the signaling molecule, the riboswitch transduces the signal into a genetic decision.

Basis for ligand discrimination between ON and OFF state riboswitch conformations: the case of the SAM-I riboswitch.

Riboswitches are RNA elements that bind to effector ligands and control gene expression. Most consist of two domains. S-Adenosyl Methionine (SAM) binds the aptamer domain of the SAM-I riboswitch and induces conformational changes in the expression domain to form an intrinsic terminator (transcription OFF state).

Design and implementation of an ribonucleic acid (RNA) directed fragment library.

The design of RNA binding ligands is complicated by issues of specificity, target flexibility, and the tractability of known RNA inhibitors toward chemical derivitization. To address these difficulties, an RNA-directed fragment compound library is presented. We began with an analysis of 120 small molecules with reported RNA-binding activity.