The prediction of reverse turns in the blue copper proteins and their copper cores

The frequencies of occurrence of the side chains in proteins in the first, second, third, and fourth positions of a reverse turn in a set of 26 nonredundant protein chains are shown in a table that lists cysteine and cystine side chains separately. This table was used to predict the reverse turns in poplar plastocyanin whose crystal structure is known (75% of the turn residues are correctly predicted but the overall accuracy of the predictions is only 66% in a turn-not-turn two-state model), and in three blue copper proteins whose crystal structures are being determined (cucumber plastocyanin and cucumber basic protein) or contemplated (Rhus vernificera stellacyanin). The copper cores proposed for cucumber basic protein and stellacyanin are discussed.