The tropical clam Lucina pectinata lives in sulfide-rich environments and is characterized by the presence of symbiotic sulfide-oxidizing bacteria that need to be supplied with both H2S and O2. The biological molecule responsible for delivering H2S to the bacteria is a heme protein called hemoglobin I (HbI). HbI is one of the few known H2S carriers in organisms that have been implicated in physiologically binding this molecule in the ferric heme iron center so as to maintain the symbiotic relationship with the bacteria as well as to protect the clam from H2S toxicity. A thorough understanding of the association, stabilization, and dissociation mechanism of the physiological relevant H2S ligand with HbI and other heme proteins has not been established yet. In this project, the relationship between structure and reactivity of the HbI-H2S complex will be investigated to define how the chemical nature of the amino acids in the heme pocket affects H2S binding and hydrogen bonding interactions in heme proteins. A combination of molecular biology and biophysical techniques will be used. In addition, correlations of HbI-H2S NMR chemical shifts and EXAFS distances of the HbI-H2S moiety will be examined. The intellectual merits of the project are to determine the structure, dynamics, and reactivity of H2S and HbI and to understand the mechanism of H2S release by the hemoglobin to the symbiotic bacteria. Understanding the biophysical basis H2S transport by HbI could help in the future developments of a biosensor to detect H2S in ecological and biological environments; H2S is a known toxic compound.
Broader Impacts: This interdisciplinary project will be used as teaching tools to mentor graduate and undergraduate students and to increase their knowledge and communication abilities to express research results to society. Consequently, the broader impacts to society are inherent to increasing the number of well-trained students capable of fully achieving their academic or industrial career. The project will also enhance outreach to pre-college students and teachers through the GK-12 program.
