TOPOLOGICAL CHIRALITY OF IRON-SULFUR PROTEINS

An examination of x-ray structures!res of single-cluster [4Fe-4S] prot eins in the Protein Data Ba nk has revealed that all redox proteins an d the glutamine 5-phosphoribosyl-1-pyrophosphate amidotransferase from Bacillus subtilis have a topological configuration arbitrarily design ated as D, whereas the DNA repair enzyme endonuclease III from Escheri chia coli has the opposite topological configuration, L. This is the f irst example in which both senses of topological chirality have been o bserved in a class of proteins. (C) 1997 John Wiley & Sons, Inc.