Heme-biosynthetic porphobilinogen deaminase protects Aspergillus nidulans from nitrosative stress.
Microorganisms have developed mechanisms to combat reactive nitrogen species (RNS); however, only a few of the fungal genes involved have been characterized. Here we screened RNS-resistant Aspergillus nidulans strains from fungal transformants obtained by introducing a genomic DNA library constructed in a multicopy vector. We found that the AN0121.3 gene (hemC) encodes a protein similar to the heme biosynthesis enzyme porphobilinogen deaminase (PBG-D) and facilitates RNS-tolerant fungal growth. The overproduction of PBG-D in A. nidulans promoted RNS tolerance, whereas PBG-D repression caused growth that was hypersensitive to RNS. PBG-D levels were comparable to those of cellular protoheme synthesis as well as flavohemoglobin (FHb; encoded by fhbA and fhbB) and nitrite reductase (NiR; encoded by niiA) activities. Both FHb and NiR are hemoproteins that consume nitric oxide and nitrite, respectively, and we found that they are required for maximal growth in the presence of RNS. The transcription of hemC was upregulated by RNS. These results demonstrated that PBG-D is a novel NO-tolerant protein that modulates the reduction of environmental NO and nitrite levels by FHb and NiR.
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Shengmin
S
Zhou
Toshiaki
T
Narukami
Misuzu
M
Nameki
Tomoko
T
Ozawa
Yosuke
Y
Kamimura
Takayuki
T
Hoshino
Naoki
N
Takaya
D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D015139:Blotting, Southern; D004271:DNA, Fungal / Q000032:analysis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015698:Genomic Library; D006418:Heme / Q000096:biosynthesis; D011163:Hydroxymethylbilane Synthase / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress; D016133:Polymerase Chain Reaction; D026361:Reactive Nitrogen Species / Q000378:metabolism*
D004271:DNA, Fungal; D005656:Fungal Proteins; D009573:Nitrites; D026361:Reactive Nitrogen Species; D009569:Nitric Oxide; D006418:Heme; D011163:Hydroxymethylbilane Synthase