DEVELOPMENT OF NOVEL INHIBITOR PROBES OF DNA POLYMERASE-III BASED ON DGTP ANALOGS OF THE HPURA TYPE - BASE, NUCLEOSIDE AND NUCLEOTIDE DERIVATIVES OF N2-(3,4-DICHLOROBENZYL)GUANINE

6-(p-Hydroxyphenylhydraxino)uracil (H-2-HPUra) is a selective and potent inhibitor of the replication-specific class III DNA polymerase (pol III) of Gr+ bacteria. Although formally a pyrimidine, H-2-HPUra derives its inhibitory activity from its specific capacity to mimic the purine nucleotide, dGTP. We describe the successful conversion of the H-2-HPUra inhibitor prototype to a bona fide purine, using N2-(benzyl)guanine (BG) as the basis. Structure-activity relationships of BGs carrying a variety of substituents on the aryl ring identified N2-(3,4-dichlorobenzyl)guanine (DCBG) as a nucleus equivalent to H-2-HPUra with respect to potency and inhibitor mechanism. DCBdGTP, the 2'-deoxyribonucleoside 5'-triphosphate form of DCBG, was synthesized and characterized with respect to its action on wild-type and mutant forms of B. subtilis DNA pol III. DCBdGTP acted on pol III by the characteristic inhibitor mechanism and formally occupied the dNTP binding site with a fit which permitted its polymerization.