Identification of the Minimal Features for VapB Antitoxin Function
VapBC is the largest family of bacterial type II toxin-antitoxin systems. VapB antitoxins are thought to regulate stress-induced dormancy and persister formation by direct inhibition of their cognate VapC toxins. Jin et al. (p. 1197–1207) identified key amino acids in the minimal VapB4 antitoxin domain required for specific binding and inhibition of its cognate VapC4 toxin from Mycobacterium tuberculosis. The results indicate that the VapB4 toxin-binding module employs a hierarchy of strong and weak interactions to specify binding and inactivation of its cognate toxin, VapC4. These findings shed light on the evolution of VapBC toxin-antitoxin systems and their potential as therapeutic targets.
Mechanistic and Evolutionary Insights into Sporulation Control by the Myxococcus xanthus dev CRISPR-Cas system
Clustered regularly interspaced short palindromic repeats (CRISPRs) are preceded by CRISPR-associated (Cas) genes, forming CRISPR-Cas systems typically involved in phage defense. The dev locus of Myxococcus xanthus includes a CRISPR-Cas system implicated in sporulation control. Rajagopalan et al. (p. 1249–1262) discovered that DevR and DevS negatively regulate DevI, a small protein that appears to inhibit sporulation when overproduced. This regulatory mechanism likely evolved recently in independent lineages. Most natural isolates lack devI, and their dev promoter appears to be nonfunctional. Many such isolates nevertheless form spores. It is speculated that dev evolution provides niche-specific adaptation of sporulation control.
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