EXTENDED X-RAY ABSORPTION FINE-STRUCTURE STUDIES OF A RETROVIRUS - EQUINE INFECTIOUS-ANEMIA VIRUS CYSTEINE ARRAYS ARE COORDINATED TO ZINC

Zinc finger arrays have been established as a critical structural feature of proteins involved in DNA recognition. Retroviral nucleocapsid proteins, which are involved in the binding of viral RNA, contain conserved cysteine-rich arrays that have been suggested to coordinate zinc. We provide metalloprotein structural data from an intact virus preparation that validate this hypothesis. Extended x-ray absorption fine structure (EXAFS) spectroscopy of well-characterized and active preparations of equine infectious anemia virus, compared with a peptide with known coordination and in combination with available biochemical and genetic data, defines a Cys3His1 coordination environment for zinc. The average of the Zn-S distances is 2.30(1) angstrom and that of the Zn-N distance (to histidine) is 2.01(3) angstrom.