Topology of globular proteins. II.

This paper continues the inquiry into the likelihood of occurrence of protein structures which are “knotted”. The probability of knotted con formations is calculated by a simple Monte Carlo method for the proteins lysozyme and ribonuclease and for an elementary bicyclic polymer. Ribonuclease shows no measurable inclination towards tangling, but some 10%. of the lysozyme conformations are knotted. The implications of this result for the role of disulfide bridge formation in protein renaturation are discussed.