"A new group of eubacterial light-driven retinal-binding proton pumps with an unusual cytoplasmic proton donor"
Microbial rhodopsins are a versatile family of photoactive retinal-binding membrane proteins which are widespread geographically and taxonomically. One of the main functions of microbial rhodopsins is outward-directed light-driven proton transport across the plasma membrane, which can provide sources of energy alternative to respiration and chlorophyll photosynthesis. Proton-pumping rhodopsins are found in Archaea (Halobacteria), multiple groups of Bacteria, numerous fungi, and some microscopic algae. This work describes a new group of efficient proteobacterial retinal-binding light-driven proton pumps which lack the carboxylic proton donor on helix C (most often replaced by Gly) but possess a unique His residue on helix B. The typical representative of the group (from Pseudomonas putida) was characterized spectroscopically and through site-directed mutagenesis, which suggested that the unique histidine at position 37 likely forms a proton-donating complex involving water molecules compensating for the loss of the carboxylic proton donor.
Dr. Hermann Eberl, Chair (Department of Mathematics and Statistics)
Dr. Leonid Brown, Advisor (Department of Physics)
Dr. Vladimir Ladizhansky, Advisory Committee (Department of Physics)
Dr. Allan Rod Merrill, Advisory Committee (Department of Physics)