Does protein A mirror image exist in solution? Outline of an experimental design aimed to detect it

Abstract

ABSTRACTThere is abundant theoretical evidence indicating that a mirror image of ProteinA may occur during the protein folding process. However, as to whether such mirror image exists in solution is an unsolved issue. Here we provide outline of an experimental design aimed to detect the mirror image of Protein A in solution. The proposal is based on computational simulations indicating that the use of a mutant of protein A, namely 01 OH, could be used to detect the mirror image conformation in solution. Our results indicate that the native conformation of the protein A should have a pKa, for the 01 OH mutant, at r06.2, while the mirror image conformation should have a pKa close to ≈7.3. Naturally, if all the population is in the native state for the 01 OH mutant, the pKa should be ≈6.2, while, if all are in the mirror image state, it would be ≈7.3, and, if it is a mixture, the pKa should be larger than 6.2, presumably in proportion to the mirror population. In addition, evidence is provided indicating the tautomeric distribution of H1O must also change between the native and mirror conformations. Although this may not be completely relevant for the purpose of determining whether the protein A mirror image exists in solution, it could provide valuable information to validate the pKa findings. We hope this proposal will foster experimental work on this problem either by direct application of our proposed experimental design or serving as inspiration and motivation for other experiments.