title: Time resolved thermodynamics associated with ligand photorelease in heme peroxidases and globins: Open access channels versus gated ligand release.
abstract: Heme proteins represent a diverse class of biomolecules responsible for an extremely diverse array of physiological functions including electron transport, monooxygenation, ligand transport and storage, cellular signaling, respiration, etc. An intriguing aspect of these proteins is that such functional diversity is accomplished using a single type of heme macrocycle based upon iron protoporphyrin IX. The functional diversity originates from a delicate balance of inter-molecular interactions within the protein matrix together with well choreographed dynamics that modulate the heme electronic structure as well as ligand entry/exit pathways from the bulk solvent to the active site. Of particular interest are the dynamics and energetics associated with the entry/exit of ligands as this process plays a significant role in regulating the rates of heme protein activity. Time-resolved photoacoustic calorimetry (PAC) has emerged as a powerful tool through which to probe the underlying energetics associated with small molecule dissociation and release to the bulk solvent in heme proteins on time scales from tens of nanoseconds to several microseconds. In this review, the results of PAC studies on various classes of heme proteins are summarized highlighting how different protein structures affect the thermodynamics of ligand migration. This article is part of a Special Issue entitled: Protein Dynamics: Experimental and Computational Approaches.
authors.affiliation: Department of Chemistry, University of South Florida, 4202 East Fowler Ave., Tampa, FL 33620, USA.
authors.forename: Carissa M
authors.initials: CM
authors.lastname: Vetromile
authors.forename: Jaroslava
authors.initials: J
authors.lastname: Miksovska
authors.forename: Randy W
authors.initials: RW
authors.lastname: Larsen
mesh_terms: D002151:Calorimetry; D006454:Hemoglobins / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry; D008024:Ligands; D010544:Peroxidases / Q000737:chemistry*; D010777:Photochemistry
chemical_list: D006454:Hemoglobins; D007473:Ion Channels; D008024:Ligands; D010544:Peroxidases