Abstract
RecA is a multifunctional protein that plays a central role in DNA repair in bacteria. The structural Make ATP Work motif (MAW) is proposed to control the ATPase activity of RecA. In the present work, we report the biochemical activity and structural effects of the L53Q mutation at the MAW motif of the RecA protein from H. seropedicae (HsRecA L53Q). In vitro studies showed that HsRecA L53Q can bind ADP, ATP, and ssDNA, as does wild-type RecA. However, the ATPase and DNA-strand exchange activities were completely lost. In vivo studies showed that the expression of HsRecA L53Q in E. coli recA1 does not change its phenotype when cells were challenged with MMS and UV. Molecular dynamics simulations showed the L53Q point mutation did not cause large conformational changes in the HsRecA structure. However, there is a difference on dynamical cross-correlation movements of the residues involved in contacts within the ATP binding site and regions that hold the DNA binding sites. Additionally, a new hydrogen bond, formed between Q53 and T49, was hypothesized to allow an independent motion of the MAW motif from the hydrophobic core, what could explain the observed loss of activity of HsRecA L53Q.
Highlights
The bacterial RecA protein plays a central role in (1) the repair of stalled replication forks and double-strand break, (2) general recombination, (3) induction of the SOS response, and (4) translesion DNA synthesis [1,2]
The temperature was lowered to 25 ̊C for 30 min and 1 mM isopropyl-β-D-thiogalactopyranoside was added to induce the expression of the His-tagged wild-type H. seropedicae RecA (HsRecA) and mutant HsRecA L53Q
Seropedicae RecA ATP hydrolysis and DNA repair for any of the RecA proteins studied, indicating that the binding of [α32P]ATP is specific to the ATP-binding site and is preserved in all proteins, including HsRecA L53Q
Summary
The bacterial RecA protein plays a central role in (1) the repair of stalled replication forks and double-strand break, (2) general recombination, (3) induction of the SOS response, and (4) translesion DNA synthesis [1,2]. Its functions in vivo depend upon several key activities identified in vitro, including the binding of DNA molecules and the hydrolysis of ATP. RecA L1 and L2 motifs form the DNA binding sites and RecA Walker A and B motifs, the ATP (or other NTPs) binding and hydrolysis site [3,4]. Seropedicae RecA ATP hydrolysis and DNA repair study design, data collection and analysis, decision to publish, or preparation of the manuscript
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