catalyzes the oxidation of sulfides, such as hydrogen sulfide, with the help of a quinone. Has the highest activity with caldariella quinone and decylubiquinone, and lower activity with naphtoquinones. •

MAKHVVVIGGGVGGIATAYNLRNLMPDLKITLISDRPYFGFTPAFPHLAMGWRKFEDISV PLAPLLPKFNIEFINEKAESIDPDANTVTTQSGKKIEYDYLVIATGPKLVFGAEGQEENS TSICTAEHALETQKKLQELYANPGPVVIGAIPGVSCFGPAYEFALMLHYELKKRGIRYKV PMTFITSEPYLGHFGVGGIGASKRLVEDLFAERNIDWIANVAVKAIEPDKVIYEDLNGNT HEVPAKFTMFMPSFQGPEVVASAGDKVANPANKMVIVNRCFQNPTYKNIFGVGVVTAIPP IEKTPIPTGVPKTGMMIEQMAMAVAHNIVNDIRNNPDKYAPRLSAICIADFGEDAGFFFA DPVIPPRERVITKMGKWAHYFKTAFEKYFLWKVRNGNIAPSFEEKVLEIFLKVHPIELCK DCEGAPGSRC 438

	PMID	Title & Author	Abstract	Year
0	30278355	A novel transcription factor Rwdd1 and its SUMOylation inhibit the expression of sqr, a key gene of mitochondrial sulfide metabolism in Urechis unicinctus. Xueyu Li , Xiaolong Liu , Zhenkui Qin , Maokai Wei , Xitan Hou , Tingting Zhang , Zhifeng Zhang	Sulfide-quinone oxidoreductase (SQR) is a key enzyme of sulfide metabolism in metazoans, and responsible for oxidizing sulfide into thiosulfate and transmitting the generated electrons to the ubiquinone. It has been revealed that the sqr mRNA level increases significantly in echiuran worm Urechis unicinctus exposed to sulfide, and HSF1, NF1 and Sp1 have been verified to participate in its transcriptional regulation. In this study, we obtained 23 potential transcription factors interacting possibly with the proximal region (-391 to +50) of sqr promoter, and focused on the RWD domain-containing 1 (Rwdd1), a protein with the maximum number of clones in yeast one-hybrid (Y1H) screening, to investigate its transcriptional regulation to U. unincitus sqr. The ChIP and EMSA assays identified that the Rwdd1 can bind directly to the promoter (+18/+36) of U. unicinctus sqr. The point mutation and transient transfection experiments discovered that TACG was the key sequence of the DNA element bound by the Rwdd1. Furthermore, the U. unicinctus Rwdd1 (UuRwdd1) was identified to be a transcription repressor inhibiting the sqr promoter activity, and the SUMOylation of UuRwdd1 at the lysine of 90th enhanced its inhibitory effect on sqr transcription further. Western blotting found Rwdd1 responded to sulfide in hindguts from U. unincitus, and the protein content showed a remarkable drop in hindgut nuclei in the early sulfide exposure, and then increased significantly both in the total protein and the nuclear protein extract. We suggested that the Rwdd1 is a novel transcription factor, and these data improve our understanding of the sqr transcriptional regulation and the mitochondrial sulfide metabolism.	2018
1	27070384	NF1, Sp1 and HSF1 are synergistically involved in sulfide-induced sqr activation in echiuran worm Urechis unicinctus. Xiaolong Liu , Zhenkui Qin , Xueyu Li , Xiaoyu Ma , Beibei Gao , Zhifeng Zhang	Sulfide is a well-known environmental toxic substance. Mitochondrial sulfide oxidation is a main mechanism of sulfide detoxification in organisms, and sulfide: quinone oxidoreductase (SQR) is a key enzyme which is involved in transferring electrons from sulfide to ubiquinone and converting sulfide into thiosulfate. Previous studies have revealed the SQR-mediated mitochondrial sulfide oxidation exists in the echiuran worm Urechis unicinctus, and its sqr mRNA level increased significantly when the worm is exposed to sulfide. In this study, we attempt to reveal the synergistic regulation of transcription factors on sulfide-induced sqr transcription in U. unicinctus.	2016
2	26675369	Sulfide exposure results in enhanced sqr transcription through upregulating the expression and activation of HSF1 in echiuran worm Urechis unicinctus. Xiaolong Liu , Zhifeng Zhang , Xiaoyu Ma , Xueyu Li , Di Zhou , Beibei Gao , Yajiao Bai	Sulfide is a natural, widely distributed, poisonous substance. Sulfide: quinone oxidoreductase (SQR) is responsible for the initial oxidation of sulfide in mitochondria. To study transcriptional regulation of sqr after sulfide exposure, a 2.6-kb sqr upstream sequence from echiuran worm Urechis unicinctus was cloned by genome walking. Bioinformatics analysis showed 3 heat shock elements (HSEs) in proximal promoter region of the sqr upstream sequence. Moreover, an Hsf1 cDNA in U. unicinctus (UuHsf1) was isolated with a full-length sequence of 2334 bp and its polyclonal antibody was prepared using U. unicinctus HSF1 (UuHSF1) expressed prokaryotically with whole sequence of its open reading frame (ORF). In vivo ChIP and in vitro EMSA assays revealed UuHSF1 could interact with the sqr proximal promoter region. Transient transfection and mutation assays indicated that UuHSF1 bound specifically to HSE (-155bp to -143bp) and enhanced the transcription of sqr. Furthermore, sulfide treatment experiments demonstrated that sulfide could increase the expression of HSF1 protein, and induce trimerization of the protein which binds to HSEs and then activate sqr transcription. Quantitative real-time PCR analysis revealed sqr mRNA level increased significantly after U. unicinctus was exposed to sulfide for 6h, which corresponded to content changes of both trimeric HSF1 and HSF1-HSE complex. We concluded that UuHSF1 is a transcription factor of sqr and sulfide could induce sqr transcription by upregulating the expression and activation of HSF1 in U. unicinctus exposed to sulfide.	2016
3	10816041	Sulfide:quinone oxidoreductase in membranes of the hyperthermophilic bacterium Aquifex aeolicus (VF5). T Nübel , C Klughammer, R Huber, G Hauska, M Schütz	The sulfide-dependent reduction of exogenous ubiquinone by membranes of the hyperthermophilic chemotrophic bacterium Aquifex aeolicus (VF5), the sulfide-dependent consumption of oxygen and the reduction of cytochromes by sulfide in membranes were studied. Sulfide reduced decyl-ubiquinone with a maximal rate of up to 3.5 micromol (mg protein)(-1) min(-1) at 20 degrees C. Rates of 220 nmol (mg protein)(-1) min(-1)] for the sulfide-dependent consumption of oxygen and 480 nmol (mg protein)(-1) min(-1) for the oxidation of sulfide at 20 C were estimated. The reactions were sensitive towards 2-n-nonyl-4-hydroxyquinoline-N-oxide, but insensitive towards cyanide. Both reduction of decyl-ubiquinone and consumption of oxygen by sulfide rapidly increased with increasing temperature. For the sulfide-dependent respiratory activity, a sulfide-to-oxygen ratio of 2.3+/-0.2 was measured. This indicates that sulfide was oxidized to the level of zero-valent sulfur. Reduction of cytochromes by sulfide was monitored with an LED-array spectrophotometer. Reduction of cytochrome b was stimulated by 2-n-nonyl-4-hydroxyquinoline-N-oxide in the presence of excess sulfide under oxic conditions. This "oxidant-induced reduction" of cytochrome b suggests that electron transport from sulfide to oxygen in A. aeolicus employs the cytochrome bc complex via the quinone pool. Comparison of the amino acid sequence with the sequence of the sulfide:quinone oxidoreductase from Rhodobacter capsulatus and of the flavocytochrome c from Allochromatium vinosum revealed that the sulfide:quinone oxidoreductase from A. aeolicus belongs to the glutathione reductase family of flavoproteins.	2000

Nübel T, Klughammer C , Huber R , et al. Sulfide:quinone oxidoreductase in membranes of the hyperthermophilic bacterium Aquifex aeolicus (VF5).[J]. Archives of Microbiology, 2000, 173(4):233-244. José A Brito, Sousa F L , Stelter M , et al. Structural and Functional Insights into Sulfide:Quinone Oxidoreductase[J]. Biochemistry, 2009, 48(24):5613-5622.