Mechanism of HIV reverse transcriptase: enzyme-primer interaction as revealed through studies of a dNTP analogue, 3'-azido-dTTP.

Abstract:

Primer and dNTP recognition by purified HIV reverse transcriptase have ...
Primer and dNTP recognition by purified HIV reverse transcriptase have been investigated. Earlier kinetic studies suggested that the reaction pathway for DNA synthesis is ordered, with template-primer and free enzyme combining to form the first complex in the reaction sequence [Majumdar et al. (1988) J. Biol. Chem. 263, 15657-15665], and through use of a particularly high affinity template-primer analogue [r(I)n.Sd(C)28], rate values for formation of the first complex were calculated [Majumdar et al. (1989) Biochemistry 28, 1340-1346]. We now report rate values for first complex formation in the usual model replication system with poly[r(A)].oligo [d(T)] as template-primer. We find that 3'-azido-dTTP (AZTTP) is a linear competitive inhibitor of DNA synthesis against the substrate dNTP (dTTP) in the poly[r(A)].oligo[d(T)] replication system. This suggests that 3'-azido-dTTP and dTTP combine with the same form of the enzyme in the reaction scheme, i.e., the enzyme-primer complex. This is not trivial, since a second analogue, 3'-amino-dTTP, also is an inhibitor against dTTP, but the mechanism in this case is linear noncompetitive. Because the inhibition by 3'-azido-dTTP is linear competitive, the KD for physical binding to the enzyme is assumed to be the same as the Ki for inhibition (20 nM). Substrate kinetic studies of DNA synthesis using 3'-azido-dTTP as substrate revealed that the Michaelis constant is 3 microM. Therefore, the Km for this substrate analogue is 100-fold higher than the KD for binding of the analogue to the enzyme-primer complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymerases:

Topics:

Status:

new topics/pols set partial results complete validated

Results:

No results available for this paper.

Entry validated by:

Using Polbase tables:

Sorting:

Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).

Filtering:

It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.