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Structure Guided Understanding of NAD+ Recognition in Bacterial DNA Ligases
journal contribution
posted on 2016-02-21, 17:23 authored by Sushmita D. Lahiri, Rong-Fang Gu, Ning Gao, Irene Karantzeni, Grant K. Walkup, Scott D. MillsNAD+-dependent DNA ligases (LigA) are essential
bacterial
enzymes that catalyze phosphodiester bond formation during DNA replication
and repair processes. Phosphodiester bond formation proceeds through
a 3-step reaction mechanism. In the first step, the LigA adenylation
domain interacts with NAD+ to form a covalent enzyme-AMP
complex. Although it is well established that the specificity for
binding of NAD+ resides within the adenylation domain,
the precise recognition elements for the initial binding event remain
unclear. We report here the structure of the adenylation domain from Haemophilus influenzae LigA. This structure is a first snapshot
of a LigA-AMP intermediate with NAD+ bound to domain 1a
in its open conformation. The binding affinities of NAD+ for adenylated and nonadenylated forms of the H. influenzae LigA adenylation domain were similar. The combined crystallographic
and NAD+-binding data suggest that the initial recognition
of NAD+ is via the NMN binding region in domain 1a of LigA.