Mutational analysis of two conserved sequence motifs in HIV‐1 reverse transcriptase

Abstract

Two tort,erred sequence motifs, oc~:urrin$ in HIV-I r~verse transeriptase~ at re,,dues II0+A 16 trod 183~190. have been studied ufinB ~ite.direeted mutall,,,tesis of the cloned llene. In particular, asp, flares at positioni 185 and 11t6 have each been rout;tied to either asparalline or glutamate, The resulting mutant proteins wer~ catalytically inactive but still able to bind th~ template.primer complex, ooly rA.oli~o tiT. Other mutations in these re|lions resulted in reduced reverse transcriptase activity but the mutation of tyrosine-183 to serlne caused a stllnifit~mt increase in the g,~ for dTTP and the K+ f,~r inhibition by 3'-azi,lotltymidine.lriphosphatc, 2+.Y-dldeox.vthymidine-tripho~phatc and phosphonoformie acid,

Reverse transcriptase activity innate to DNA polymerase I and DNA topoisomerase I proteins of Streptomyces telomere complex

“…that an Asp-Asp doublet-encoding sequence is included in the consensus RT motif (as motif C) present in the catalytic subunit of eukaryotic telomerases and in the HIV-RT (16,17); furthermore, mutation of this doublet abolishes the RNA-dependent DNA polymerase activity of both telomerase and HIV-RT (16,17). Accordingly, we replaced the Asp-Asp doublets at positions 464-465 and 471-472 in the Streptomyces TopA protein with Ala-Ala doublets and, remarkably, found that the resulting protein failed to show detectable RT activity (Fig.…”

“…We report here that the telomere complex of Streptomyces linear replicons also includes DNA polymerase and DNA topoisomerase proteins essential to Streptomyces propagation and, remarkably, that both of these eubacterial enzymes can function efficiently as RTs in addition to having the biochemical properties predicted from their sequences. We further show that the Streptomyces coelicolor and Streptomyces lividans TopA proteins are prototypes for a subfamily of bacterial topoisomerases whose catalytic domains contain a unique AspAsp doublet motif that is required for their RT activity and which is essential also to the RNA-dependent DNA polymerase functions of HIV RT and eukaryotic cell telomerases (16,17). (15) was amplified by using a pair of primers: 5Ј-AAACATAT-GCATCATCATCATCATCATGTGTCCGGTAGAGGAGC-GCAG-3Ј and 5Ј-GCCGTTGCCGAACAGGCTCAT-3Ј, and the amplicon was inserted into the NdeI͞EcoRI-digested pHZ1272 vector (Z. Deng, personal communication), generating plasmid pBC174.…”

“…RT assays were carried out in 20-l reaction mixtures containing 20 mM Tris⅐HCl (pH 8.0), 100 mM NaCl, 1 mM DTT, 1 mM MgCl 2 , 50 ng͞ l poly(rA)-(dT) [12][13][14][15][16][17][18] (Amersham Pharmacia), 10 Ci (1 Ci ϭ 37 GBq) of [ 32 P]dTTP (Amersham Pharmacia), and 1-l volumes of protein fractions. Reaction mixtures were incubated at 37°C for 45 min, stopped by addition of 10 l of 200 mM EDTA, and purified by using MicroSpin S-200 HR columns (Amersham Pharmacia).…”

Analysis of mutations at positions 115 and 116 in the dNTP binding site of HIV-1 reverse transcriptase

“…In analyzing mutations at Tyr-115, several groups have found that the only amino acid substitution that has little deleterious effect on the enzyme is Tyr-115-Phe (7)(8)(9)(10)(11)(12)(13)(14). Substitution of Tyr-115 with polar amino acids is extremely deleterious (9)(10)(11)(12)(13) whereas substitution with hydrophobic amino acids usually has an intermediate effect (7,8,11,12,14).…”

“…Substitution of Tyr-115 with polar amino acids is extremely deleterious (9)(10)(11)(12)(13) whereas substitution with hydrophobic amino acids usually has an intermediate effect (7,8,11,12,14). Recently, the Tyr-115-Phe mutation, along with the mutations Lys-65-Arg, Leu-74-Val, and Met-184-Val, has been detected in HIV-1 RTs resistant to the carbocyclic nucleoside analog 1592U89 (abacavir) (15,16).…”