Kamal K. Joshi/sandbox 1

IntroductionIntroduction

RcdA was first identified as a regulator for CtrA degradation, a master regulator in Caulobacter crescentus (McGrath et al., 2006). It was shown to be important for the regulated degradation of CtrA, a replication inhibitor and transcriptional activator, during swarmer to stalked transition of Caulobacter life cycle. Later in 2009, the crystal structure was solved at 2.9 A resolution(Taylor et al., 2009) yet the true function of RcdA has not been assigned to date. We at the Chien lab are working towards understanding the role of RcdA in regulated proteolysis of different key regulators in the model organism Caulobacter [[1]]

spinqualitylabelsall models RcdA: A facilitator for proteolysis of key cell-cycle regulators Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Biological state of RcdABiological state of RcdA

RcdA exist as a homodimer in solution shown by size exclusion chromatography and further supported by crystal structure (Taylor et al., 2009). The monomeric unit consists of a three-helix bundle with three disordered regions. Both monomeric units pack each other in a 2-fold symmetric orientation. Each monomeric subunit is shown in light red and blue in figure shown at the right.

spinqualitylabelsall models RcdA displaying conservation of residues across different bacteral species Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Conservation of RcdAConservation of RcdA

RcdA is mostly conserved across gram-negative alpha-proteobacteria. This further lead us to hypothesize that RcdA plays an important role in the regulatory processes in Caulobacter. The conservation of different residues as predicted by Consurf software is shown in the diagram at the right. Clearly residues are more conserved at the dimer interface than on the surface indicating dimerization could to be the key for it to function. The color scheme representing the conservation scores is shown below.

References: 1. Patrick T. McGrath, Antonio A. Iniesta, Kathleen R. Ryan, Lucy Shapiro and Harley H. McAdams. " A Dynamically Localized Protease Complex and a Polar Specificity Factor Control a Cell Cycle Master Regulator". Cell, (2006) 124, 535–547. 2. James A. Taylor, Jeremy D. Wilbur, Stephen C. Smith and Kathleen R. Ryan. "Mutations that Alter RcdA Surface Residues Decouple Protein Localization and CtrA Proteolysis in Caulobacter crescentus". J. Mol. Biol. (2009) 394,46–60.