FIG. 39.12

What is the molecular structure of hemoglobin and myoglobin?

BACKGROUND In the 1950s, the Austrian Max Perutz worked with John Kendrew in the Cavendish Laboratory of the University of Cambridge to determine the molecular structure of globular proteins. Perutz and Kendrew were interested in understanding how the structures of hemoglobin and myoglobin enabled binding and transport of O₂.

EXPERIMENT Perutz and Kendrew developed and applied the new technique of X-ray crystallography to determine the three-dimensional molecular structures of hemoglobin and myoglobin.

RESULTS Perutz and Kendrew showed that adult hemoglobin consists of four subunits, two α (alpha) and two β (beta) subunits. Each subunit contains a heme group that contains iron, which is the site of O₂ binding. By contrast, myoglobin consists of only a single subunit with one heme group. These differences in molecular structure underlie the O₂-binding and dissociation properties of the two O₂ transport proteins.

FOLLOW-UP WORK Work by Perutz in the 1960s showed how the molecular structure of hemoglobin changes when it binds O₂. Perutz also supervised Francis Crick as a doctoral student (Crick later worked with James Watson to resolve the structure of DNA). Perutz and Kendrew received the 1962 Nobel Prize in Chemistry for their work.

SOURCES Kendrew J. C., and M. F. Perutz. 1948. “A Comparative X-Ray Study of Foetal and Adult Sheep Haemoglobins.” Proceedings of the Royal Society, London, Series A 194:375–98; Perutz, M. F. 1964. “The Hemoglobin Molecule.” Scientific American 211:64–76; Perutz, M. F. 1978. “Hemoglobin Structure and Respiratory Transport.” Scientific American 239:92–125.