AUTHOR=Li Moran , Yin Jing , Mei Sha , Wang Xuhong , Tang Xiao-Feng , Tang Bing 

TITLE=Halolysin SptA, a Serine Protease, Contributes to Growth-Phase Transition of Haloarchaeon Natrinema sp. J7-2, and Its Expression Involves Cooperative Action of Multiple Cis-Regulatory Elements

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01799

DOI=10.3389/fmicb.2018.01799

ISSN=1664-302X

ABSTRACT=<p>Many haloarchaea produce extracellular subtilisin-like proteases (halolysins) during late log phase; however, the physiological function and regulatory mechanism of growth phase-dependent production of halolysins are unknown. Halolysin SptA, the major extracellular protease of <italic>Natrinema</italic> sp. J7-2, is capable of intracellular self-activation to affect haloarchaeal growth. Here, we report that deletion of <italic>sptA</italic> leads to loss of extracellular and intracellular protease activities against azocasein and/or suc-AAPF-pNA, as well as a change in growth-phase transition of the haloarchaeon. Our results suggest that SptA is important for strain J7-2 to enter the stationary and death phases. Deletion and mutational analyses of the 5′-flanking region of <italic>sptA</italic> revealed two partially overlapping, semi-palindromic sequences upstream of the TATA box act as positive and negative <italic>cis</italic>-regulatory elements, respectively, to mediate <italic>sptA</italic> expression in late log phase. Additionally, a negative <italic>cis</italic>-regulatory element covering WW motif and a distant enhancer contribute to the modulation of <italic>sptA</italic> expression. Our results demonstrate that SptA functions both extracellularly and intracellularly, and that <italic>sptA</italic> expression relies on the cooperative action of multiple <italic>cis</italic>-regulatory elements, allowing SptA to exert its function properly at different growth stages in strain J7-2.</p>