FIG. 8.
(A) Amino acid sequence alignments comparing the region surrounding the putative 3,4-heptad repeat (possible coiled-coil) region in Rep68/78 with similar regions in other parvovirus replication proteins and the Rep homolog encoded by HHV6. Sequences shown are of proteins from MDPV (71), B19 (45), HHV6 (54), GPV (71), and MVM (2). The sequences were aligned with the aid of the BestFit local alignment program (49). The alignments shown are the relevant portions of the predicted heptad repeat structure in the Rep68/78 proteins. The bold letters represent the conserved hydrophobic amino acids. Charged residues which were converted to alanine in mutants are underlined. Prolines are shown with outlined letters. The heptad repeat unit is indicated by lowercase letters (a to g). Residues at the a and d positions of the heptad repeat unit form the hydrophobic interface, while those at positions e and g participate in the formation of stabilizing salt bridges (11) and the specificity of helical interaction (58). Putative heptad repeat units for each protein are boxed and denoted I to IV. (B) Schematic of the relative positions of the amino acids with respect to the central axis of the putative helix (42).