Filling a cavity dramatically increases pressure stability of the c-Myb R2subdomain

Cavities or packing defects in proteins may generally be related with the d ynamics and function of a protein. In the c-Myb R2 subdomain, its single ca vity has been shown to be crucial for its DNA recognition. Cavities are als o considered important in determining the pressure stability of a protein. In the present work, high-pressure proton nuclear magnetic resonance (H-1 N MR) spectroscopy at 750 MHz is used to study the effect of a cavity-filling . mutation (V103L) on the stability of the c-Myb R2 subdomain in the pressu re range between I and 3,700 bar at 5 degreesC. A dramatic increase in the pressure stability of the c-Myb R2 subdomain is attained, from which we est imate the cavity size to be 35.3 Angstrom (3), in good agreement with liter ature values. We also evaluated the increase in thermodynamic stability Del taG(1bar)(0) from 5.35 kJ/mol to 7.34 kJ/mol by the mutation, giving a clea r example of the effect of a cavity on the global stability of a globular p rotein. (C) 2001 Wiley-Liss, Inc.