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Primer initiation and extension by T7 DNA primase.

Authors
Type
Published Article
Journal
The EMBO journal
Publication Date
Volume
25
Issue
10
Pages
2199–2208
Identifiers
PMID: 16642036
Source
Medline
License
Unknown

Abstract

T7 DNA primase is composed of a catalytic RNA polymerase domain (RPD) and a zinc-binding domain (ZBD) connected by an unstructured linker. The two domains are required to initiate the synthesis of the diribonucleotide pppAC and its extension into a functional primer pppACCC (de novo synthesis), as well as for the extension of exogenous AC diribonucleotides into an ACCC primer (extension synthesis). To explore the mechanism underlying the RPD and ZBD interactions, we have changed the length of the linker between them. Wild-type T7 DNA primase is 10-fold superior in de novo synthesis compared to T7 DNA primase having a shorter linker. However, the primase having the shorter linker exhibits a two-fold enhancement in its extension synthesis. T7 DNA primase does not catalyze extension synthesis by a ZBD of one subunit acting on a RPD of an adjacent subunit (trans mode), whereas de novo synthesis is feasible in this mode. We propose a mechanism for primer initiation and extension based on these findings.

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