AUTHOR=Kim Dukyun , Na Eun Jung , Kim Suhyeon , Kim Jung Sung , Jung Young Hyun , Cao Jiafu , Han Ho Jae , Bang Iel Soo , Yoo Jin-Wook , Ha Nam-Chul , Choi Sang Ho 

TITLE=Transcriptomic Identification and Biochemical Characterization of HmpA, a Nitric Oxide Dioxygenase, Essential for Pathogenesis of Vibrio vulnificus

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02208

DOI=10.3389/fmicb.2019.02208

ISSN=1664-302X

ABSTRACT=<p>Nitric oxide (NO) and its derivatives are important effectors of host innate immunity, disrupting cellular function of infecting pathogens. Transcriptome analysis of <italic>Vibrio vulnificus</italic>, an opportunistic human pathogen, identified a set of genes induced upon exposure to NO. Among them, <italic>VvhmpA</italic> (<italic>V. vulnificus hmpA</italic>), encoding a multidomain NO dioxygenase, was the most greatly induced upon exposure to NO and was thus further characterized. Absorption spectra demonstrated that <italic>Vv</italic>HmpA is a heme protein in which the heme iron can exist in either reduced, NO-bound, or oxidized state. Biochemical studies revealed that <italic>Vv</italic>HmpA is a flavohemoglobin containing equimolar amounts of heme and FAD as cofactors. The <italic>K</italic><sub>M</sub> and <italic>k</italic><sub>cat</sub> values of <italic>Vv</italic>HmpA for NO at 37°C, the temperature encountered by <italic>V. vulnificus</italic> in the host, were greater than those at 30°C, indicating that <italic>Vv</italic>HmpA detoxifies high levels of NO effectively during infection. Compared with the wild type, the <italic>VvhmpA</italic> mutant exhibited a lower NO-decomposition activity and impaired growth in the presence of NO <italic>in vitro</italic>. Also, the cytotoxicity and survival of the <italic>VvhmpA</italic> mutant infecting the NO-producing murine macrophage cells were lower than those of the wild type. Furthermore, the mouse lethality of the <italic>VvhmpA</italic> mutant was reduced compared to that of the parental wild type. The combined results revealed that <italic>Vv</italic>HmpA is a potent virulence factor that is induced upon exposure to NO and important for the survival and pathogenesis of <italic>V. vulnificus</italic> during infection.</p>