Kinetic Pathways and Barriers for Ligand Binding to Myoglobin

Myoglobin is a small globular heme protein that increases the aerobic capacity of striated vertebrate muscle cells by taking up oxygen from blood during rest and delivering O2 to mitochondria during muscle contraction when blood flow through capillaries is restricted. The ferrous form of myoglobin can also react with CO and NO, which are produced in vivo as second messengers for regulating various physiological functions including blood pressure, platelet aggregation, and neurotransmission. Its tertiary structure consists of eight tightly packed helices, and the resulting “myoglobin fold” is very similar to that found for the α and β subunits of hemoglobin.