The long-term objective of this proposal is to understand how heme protein architecture regulates heme protein reactivity. The project has as its focus the Glycera dibranchiata monomer hemoglobins. There are three distinct monomer hemoglobins two of which exhibit structures similar to vertebrate myoglobins. Despite this their kinetic properties differ significantly from myoglobin, for the probable reason that in each of the monomer hemoglobins the distal histidine is replaced by leucine. In the case of cyanide binding, for example, these proteins are notably unreactive in comparison to vertebrate myoglobins. One of these globin cDNA sequences has been cloned, sequenced and expressed in an E. coli expression system. Site-directed mutants have also been constructed to see if enhanced reactivity can be built in to a naturally unreactive structure. Wild-type proteins and site directed mutants will be studied using kinetics, equilibrium and NMR to fulfill the goal of relating structure to function.
