The DNA transporter ComEC has metal‐dependent nuclease activity that is important for natural transformation

• Published in: Molecular microbiology Vol. 116; no. 2; pp. 416 - 426
• Main Authors: Silale, Augustinas, Lea, Susan M., Berks, Ben C.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2021; John Wiley and Sons Inc
• Subjects: Bacillus subtilis - genetics; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological Transport, Active - genetics; Biological Transport, Active - physiology; competence; Cytoplasmic membranes; Deoxyribonucleases - metabolism; Deoxyribonucleic acid; DNA; DNA Transformation Competence - genetics; DNA transporter; Enzymatic activity; Genomes; Gram‐positive bacteria; Homology; Imports; Inactivation; Manganese ions; Metallography; Multienzyme Complexes - genetics; Multienzyme Complexes - metabolism; natural transformation; Nuclease; Phosphodiesterase; Phosphoric Diester Hydrolases - metabolism; Proteins; Transformation, Bacterial - genetics; Transformations (mathematics); Gram-positive bacteria; competence; DNA transporter; nuclease; natural transformation
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14720

In the process of natural transformation bacteria import extracellular DNA molecules for integration into their genome. One strand of the incoming DNA molecule is degraded, whereas the remaining strand is transported across the cytoplasmic membrane. The DNA transport channel is provided by the protein ComEC. Many ComEC proteins have an extracellular C‐terminal domain (CTD) with homology to the metallo‐β‐lactamase fold. Here we show that this CTD binds Mn2+ ions and exhibits Mn2+‐dependent phosphodiesterase and nuclease activities. Inactivation of the enzymatic activity of the CTD severely inhibits natural transformation in Bacillus subtilis. These data suggest that the ComEC CTD is a nuclease responsible for degrading the nontransforming DNA strand during natural transformation and that this process is important for efficient DNA import. During natural transformation in bacteria one DNA strand is transported into the cytoplasm via the membrane protein ComEC while the other strand is degraded. Here we show that the C‐terminal domain of ComEC has a nuclease activity that is important for natural transformation in B. subtilis. Thus, this domain is likely to be responsible for digesting the non‐transforming DNA strand.