Abstract
SummaryBacteriophage possess a variety of auxiliary metabolic genes of bacterial origin. These proteins enable them to maximize infection efficiency, subverting bacterial metabolic processes for the purpose of viral genome replication and synthesis of the next generation of virion progeny. Here, we examined the enzymatic activity of a cyanophage MazG protein – a putative pyrophosphohydrolase previously implicated in regulation of the stringent response via reducing levels of the central alarmone molecule (p)ppGpp. We demonstrate, however, that the purified viral MazG shows no binding or hydrolysis activity against (p)ppGpp. Instead, dGTP and dCTP appear to be the preferred substrates of this protein, consistent with a role preferentially hydrolysing deoxyribonucleotides from the high GC content host Synechococcus genome. This showcases a new example of the fine‐tuned nature of viral metabolic processes.
Highlights
Cyanophage that infect the marine cyanobacterial genera Synechococcus and Prochlorococcus are widespread and abundant in oceanic systems (Suttle and Chan 1994; Sullivan et al, 2003; Baran et al, 2018) where they play important ecosystem roles including releasing organic matter through cell lysis (Suttle, 2007), transferring genes horizontally between hosts (Zeidner et al, 2005) and structuring host communities (Muhling et al, 2005)
Picocyanobacteria encode two genes annotated as MazG, a „large‟ MazG version similar to that found in most bacteria, and a „small‟ version which is similar in size to the cyanophage gene (Fig. 2)
In order to assess the hydrolytic activity of the host and cyanophage MazG proteins we cloned into E. coli, over-expressed and purified the host Synechococcus sp
Summary
Cyanophage that infect the marine cyanobacterial genera Synechococcus and Prochlorococcus are widespread and abundant in oceanic systems (Suttle and Chan 1994; Sullivan et al, 2003; Baran et al, 2018) where they play important ecosystem roles including releasing organic matter through cell lysis (Suttle, 2007), transferring genes horizontally between hosts (Zeidner et al, 2005) and structuring host communities (Muhling et al, 2005). Cyanophage can influence ocean biogeochemistry by modifying host metabolism during the infection process, such as the shutdown of CO2 fixation whilst maintaining photosynthetic electron transport (Puxty et al, 2016). This subversion of host metabolism is facilitated by the expression of cyanophage genes that appear to have a bacterial origin, so-called auxiliary metabolic genes (AMGs) (Breitbart et al, 2007). Amongst the cyanophage AMGs MazG is a core gene in cyanomyoviruses (Millard et al, 2009; Sullivan et al, 2010) and of particular interest since it has been proposed to play a more general role in regulating host metabolism (Clokie and Mann 2006; Clokie et al, 2010). In Escherichia coli MazG has been implicated in regulating programmed cell death by interfering with the function of the MazEF toxinantitoxin system, through lowering of cellular (p)ppGpp levels (Gross et al, 2006)
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