AUTHOR=Stuart Rhona K. , Brahamsha Bianca , Palenik Brian TITLE=A Deg-protease family protein in marine Synechococcus is involved in outer membrane protein organization JOURNAL=Frontiers in Marine Science VOLUME=1 YEAR=2014 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2014.00016 DOI=10.3389/fmars.2014.00016 ISSN=2296-7745 ABSTRACT=

Deg-family proteases are a periplasm-associated group of proteins that are known to be involved in envelope stress responses and are found in most microorganisms. Orthologous genes SYNW2176 (in strain WH8102) and sync_2523 (strain CC9311) are predicted members of the Deg-protease family and are among the few genes induced by copper stress in both open ocean and coastal marine Synechococcus strains. In contrast to the lack of a phenotype in a similar knockout in Synechocystis PCC6803, a SYNW2176 knockout mutant in strain WH8102 was much more resistant to copper than the wild-type. The mutant also exhibited a significantly altered outer membrane protein composition which may contribute to copper resistance, longer lag phase after transfer, low-level consistent alkaline phosphatase activity, and an inability to induce high alkaline phosphatase activity in response to phosphate stress. This phenotype suggests a protein-quality-control role for SYNW2176, the absence of which leads to a constitutively activated stress response. Deg-protease family proteins in this ecologically important cyanobacterial group thus help to determine outer membrane responses to both nutrients and toxins.