Nov 1, 1975

Intramolecular arsanilazotyrosine-248-Zn complex of carboxypeptidase A: a monitor of multiple conformational states in solution

Proceedings of the National Academy of Sciences of the United States of America
L W HarrisonB L Vallee


The red azoTyr-248-Zn complex of arnilazocarboxypeptidase, previously used to demonstrate differences in conformation of the enzyme in crystals and in solution, has now provided means to detect multiple conformations of the enzyme in solution by stopped-flow pH and temperature jump experiments. These studies identify two distinct processes. Er + H+ in equilibrium Ey (I), is the extremely rapid, Kfast about 10(5) sec-1, pH dependent dissociation of the metal complex. Ey in equilibrium Ey' (II), is much slower, Kslow about 5 sec-1, pH independent interconversion of two distinct populations of protein molecules, Ey and Ey', in which the yellow azo-Tyr-248 is different conformations. These two conformations can be differentiated readily by stopped-flow pH-jump experiments, since I is three to four orders of magnitude faster than II. Mathematical expressions derived from this mechanism accurately predict all observations over the pH range from 6.0 to 8.5. In a previous stopped-flow pH-jump experiment, Lipcomb and coworkers [Quiocho, F. A., McMurray, C. H. & Lipcomb, W. H. (1972), Proc. Nat. Acad. Sci. USA 69, 2850-2854] recognized only a single process with a rate constant of about 6 sec-1, but not the major, very rapid rate observe...Continue Reading

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Mentioned in this Paper

Carboxypeptidase A
Crystal - Body Material
Activated T Cell Autonomous Cell Death
Enzymes, antithrombotic
Structure-Activity Relationship
Plain X-ray
Carboxypeptidase A Activity
Cell Differentiation Process
Temperature Jump

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