Interpretation of some Conformational Data in Myoglobin and Lysozyme

Abstract

THE conformations of the polypeptide chains of myoglobin¹ and lysozyme² have been successfully simulated with the aid of computed Van der Waals contact and energy maps of the theoretical independent peptide unit (IPU)^3–5. The non-glycyl experimental points plotted on an alanyl IPU are rather scattered on the allowed conformational regions of the map⁶, especially in the case of lysozyme. By contrast, well defined clusters of points can be observed when only the amino-acid residues in segments of the helical secondary structure (mainly α and β chains) are plotted. In addition, clusters of points, albeit less well defined, can be observed by plotting the points relative to the experimental conformations of the first non-helical amino-acid residue next to a more or less folded segment of that α-helical type so frequently present in globular proteins (Fig. 1).