Alternative Theories on How Hemoglobins and Other Allosteric Proteins Work

Alternative Theories on How Hemoglobins and Other Allosteric Proteins Work 

Two quite different models were proposed about 25 years ago to explain the unusual nature of the hemoglobin oxygen-binding curve (fig. 5.14). These models can also be used as a starting point for discussing other allosteric proteins. The first model, introduced by Jacque Monod, Jeffery Wyman, and Pierre Changeux in 1965, is called the symme- 

Alternative models for hemoglobin allostery, (a) In the symmetry model hemoglobin can exist in only two states. (b) In the sequential model hemoglobin can exist in a number of different states. Only the subunit binding oxygen must be in the high-affinity form. 

The hierarchy of muscle organization. A voluntary muscle such as the bicep is a composite of many fibers connected to tendons at both ends. Each muscle fiber is composed of several myofibrils that are surrounded by an electrically excitable membrane (sarcolemma). 

Myofibrils exhibit longitudinally repeating structures called sarcomeres. The fine structure of the sarcomere is described in figure 5.16. 

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Alternative Theories on How Hemoglobins and Other Allosteric Proteins Work Muscle Is an Aggregate of Proteins Involved in Contraction... 

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