DOES A BACKWARDLY READ PROTEIN-SEQUENCE HAVE A UNIQUE NATIVE-STATE

Amino acid sequences of native proteins are generally not palindromic, Nevertheless, the protein molecule obtained as a result of reading th e sequence backwards, i.e. a retro-protein, obviously has the same ami no acid composition and the same hydrophobicity profile as the native sequence, The important questions which arise in the context of retro- proteins are: does a retro-protein fold to a well defined native-like structure as natural proteins do and, if the answer is positive, does a retro-protein fold to a structure similar to the native conformation of the original protein? In this work, the fold of retro-protein A, o riginated from the retro-sequence of the B domain of Staphylococcal pr otein A, was studied, As a result of lattice model simulations, it is conjectured that the retro-protein A also forms a three-helix bundle s tructure in solution, It is also predicted that the topology of the re tro-protein A three-helix bundle is that of the native protein A, rath er than that corresponding to the mirror image of native protein A, Se condary structure elements in the retro-protein do not exactly match t heir counterparts in the original protein structure; however, the amin o acid side chain contact pattern of the hydrophobic core is partly co nserved.