THE CRITICAL C-TERMINUS OF THE SMALL-SUBUNIT OF HERPES-SIMPLEX VIRUS RIBONUCLEOTIDE REDUCTASE IS MOBILE AND CONFORMATIONALLY SIMILAR TO C-TERMINAL PEPTIDES

The C-terminus of the small subunit of class I ribonucleotide reductas es is essential for subunit association and enzymatic activity. H-1 NM R analysis of the small subunit (2 x 38 kDa as a homodimer) of herpes simplex virus ribonucleotide reductase shows that this critical bindin g site is mobile and exposed in relation to the rest of the protein. A ssignments of six C-terminal amino acids are made by comparing the TOC SY and NOESY spectra of the small subunit with the spectra of an ident ical protein truncated by seven amino acids at the C-terminus and the spectra of an analogous 15 amino acid peptide. The mobility of the C-t erminus may be important for subunit recognition and could be general for other ribonucleotide reductases. The spectral comparisons also sug gest that the six C-terminal amino acids of the small subunit and pept ide are conformationally similar. This observation may be important fo r the design of inhibitors of ribonucleotide reductase subunit associa tion. (C) Munksgaard 1994.