Several bacterial pathogens require the "twitching" motility produced by filamentous type IV pili (T4P) to establish and maintain human infections. Two cytoplasmic ATPases function as an oscillatory motor that powers twitching motility via cycles of pilus extension and retraction. The regulation of this motor, however, has remained a mystery. In a collaborative work published in PNAS, members of the Redinbo Group have discovered that a single atom – a calcium, in fact – can control how bacteria walk.
By resolving the structure of a protein involved in the movement of the opportunitistic human pathogen Pseudomonas aeruginosa, the scientists identified a spot on the bacteria, that when blocked, can stop it in its tracks. The finding identifies a key step in the process by which bacteria infect their hosts, and could one day lead to new drug targets to prevent infection.
As published in the Journal of Molecular Biology, in collaboration with researchers from UNC's Department of Biology, investigators in the Redinbo Group show how the majority of eukaryotic pre-mRNAs are processed by 3'-end cleavage and polyadenylation. The complex responsible contains the ~1160-residue protein Symplekin. The structure and dynamics of the Symplekin N-terminal HEAT domain were investigated to begin elucidating the role Symplekin plays in mRNA maturation. The crystal structure of the Drosophila melanogaster Symplekin HEAT domain was determined to 2.4 Å resolution with single-wavelength anomalous dispersion phasing methods.
Molecular dynamics simulations of this domain show that the presence of a unique loop dampens correlated and anticorrelated motion in the HEAT domain, therefore providing a neutral surface for potential protein–protein interactions. HEAT domains are often employed for such macromolecular contacts. Together, these data support the conclusion that the Symplekin HEAT domain serves as a scaffold for protein–protein interactions essential to the mRNA maturation process.
The Redinbo Laboratory has demonstrated that nuclear receptor ligand binding domains move in a cohesive fashion to enhance the active conformation of their key surface protein-protein interaction sites.
Using molecular dynamics simulations and computational biology, graduate students Denise Teotico and Monica Frazier showed that such motions are long-range, encompassing distances larger than 40 Å, and are present in receptors as distinct as the estrogen receptor and the nuclear xenobiotic receptor PXR.
Graduate student Andrew Hemmert in the Redinbo Group, has been selected to receive a Graduate Education Advancement Board Impact Award. This award, sponsored by the Graduate School's external advancement board of private citizens, recognizes outstanding graduate student research of particular benefit to North Carolina. The Impact Awards Selection Committee, comprised of faculty from across campus, reviewed a large number of exemplary applications. Andrew's project was selected as having exceptional quality and impact.
Andrew's research focuses on treatment options against nerve agent chemical weapons, some of the deadliest compounds ever created by man. Current treatments for nerve agent poisoning offer only limited protection and must be administered rapidly to be effective. An ideal treatment would be an intervention capable of quickly destroying a broad range of nerve agents. Andrew has developed a protein-based therapy with the enhanced ability to detoxify nerve agents up to 10,000-fold faster than current treatments. This designed protein is considered by the U.S. military to be a promising therapy candidate for nerve agent protection, and Andrew is now developing these reagents into injectable therapeutics to protect at-risk personnel, along with miniaturized detectors to alert troops to the presence of specific nerve agents. The goal of his research is to provide an array of commercial products designed to advance North Carolina's biotechnology industry and save the lives of soldiers.
As reported by researchers in the Redinbo Group, TraI relaxase–helicase is the central catalytic component of the multiprotein relaxosome complex responsible for conjugative DNA transfer (CDT) between bacterial cells. CDT is a primary mechanism for the lateral propagation of microbial genetic material, including the spread of antibiotic resistance genes. The 2.4-Å resolution crystal structure of the C-terminal domain of the multifunctional Escherichia coli F (fertility) plasmid TraI protein is presented, and specific structural regions essential for CDT are identified.
The crystal structure reveals a novel fold composed of a 28-residue N-terminal α-domain connected by a proline-rich loop to a compact α/β-domain. Both the globular nature of the α/β-domain and the presence as well as rigidity of the proline-rich loop are required for DNA transfer and single-stranded DNA binding. Taken together, these data establish the specific structural features of this noncatalytic domain that are essential to DNA conjugation.
In a paper published in Science, researchers report that they resurrected a protein from ancient fish that swam the oceans some 450 million years ago and retraced the step-wise process by which it evolved into its modern form. UNC structural biologist Matt Redinbo compared the modern and ancient proteins and, through some deft detective work, crafted a detailed "movie" of the exact sequence of mutations that enabled the ancestral protein to take on new modern functions.