미생물학회지 (Korean Journal of Microbiology)

  • 제55권2호
  • /
  • Pages.123-130
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  • 2019
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  • 0440-2413(pISSN)
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  • 2383-9902(eISSN)
한국미생물학회 (The Microbiological Society of Korea)
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Bacillus subtilis subsp. spizizenii의 sirohydrochlorin chelatase SirB의 코발트 복합체 구조

Cobalt complex structure of the sirohydrochlorin chelatase SirB from Bacillus subtilis subsp. spizizenii

  • 남미선 (강원대학교 의생명과학대학 의생명융합학부) ;
  • 송완석 (강원대학교 의생명과학대학 의생명융합학부) ;
  • 박순철 (강원대학교 의생명과학대학 의생명융합학부) ;
  • 윤성일 (강원대학교 의생명과학대학 의생명융합학부)
  • Nam, Mi Sun (Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University) ;
  • Song, Wan Seok (Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University) ;
  • Park, Sun Cheol (Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University) ;
  • Yoon, Sung-il (Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University)
  • 투고 : 2019.04.22
  • 심사 : 2019.06.05
  • 발행 : 2019.06.30
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초록

Chelatase는 tetrapyrrole에 2가 금속을 삽입하는 데 관여하는 효소로서 cobalamin, siroheme, heme, chlorophyll과 같은 금속-tetrapyrrole의 생합성에 필수적인 역할을 담당한다. SirB는 sirohydrochlorin(SHC) tetrapyrrole의 중앙부에 코발트나철을 삽입하여 코발트-SHC 또는 철-SHC를 형성하는 SHC chelatase이다. SirB의 금속 결합 기전 및 SHC 인식 기전을 구조적으로 이해하기 위해 Bacillus subtilis subsp. spizizenii에서 유래한 SirB(bssSirB)의 코발트 복합체 구조를 규명하였다. bssSirB는 N-말단 도메인(NTD)과 C-말단 도메인(CTD)으로 구성된 ${\alpha}/{\beta}$ 단량체 구조를 형성한다. bssSirB는 NTD와 CTD 사이에 서열 보존성이 높은 공동을 지니며 NTD의 histidine 잔기 2개를 이용하여 공동 상단에서 코발트 이온과 상호작용한다. 또한 구조 비교 분석 결과 bssSirB는 공동 내에 SHC 분자를 수용하는 것으로 판단된다. 이러한 구조적 발견에 기초하여 bssSirB의 공동은 SHC의 코발트 삽입이 이뤄지는 활성 부위임을 제안한다.

Chelatase catalyzes the insertion of divalent metal into tetrapyrrole and plays a key role in the biosynthesis of metallated tetrapyrroles, such as cobalamin, siroheme, heme, and chlorophyll. SirB is a sirohydrochlorin (SHC) chelatase that generates cobalt-SHC or iron-SHC by inserting cobalt or iron into the center of sirohydrochlorin tetrapyrrole. To provide structural insights into the metal-binding and SHC-recognition mechanisms of SirB, we determined the crystal structure of SirB from Bacillus subtilis subsp. spizizenii (bssSirB) in complex with cobalt ions. bssSirB forms a monomeric ${\alpha}/{\beta}$ structure that consists of two domains, an N-terminal domain (NTD) and a C-terminal domain (CTD). The NTD and CTD of bssSirB adopt similar structures with a four-stranded ${\beta}-sheet$ that is decorated by ${\alpha}-helices$. bssSirB presents a highly conserved cavity that is generated between the NTD and CTD and interacts with a cobalt ion on top of the cavity using two histidine residues of the NTD. Moreover, our comparative structural analysis suggests that bssSirB would accommodate an SHC molecule into the interdomain cavity. Based on these structural findings, we propose that the cavity of bssSirB functions as the active site where cobalt insertion into SHC occurs.

키워드

MSMHBQ_2019_v55n2_123_f0001.png 이미지

Fig. 1. Sequence and biochemical characterization of bssSirB.

MSMHBQ_2019_v55n2_123_f0002.png 이미지

Fig. 2. Crystal structure of bssSirB.

MSMHBQ_2019_v55n2_123_f0003.png 이미지

Fig. 3. Cobalt ions in the crystal structure of bssSirB.

MSMHBQ_2019_v55n2_123_f0004.png 이미지

Fig. 4. Sequence conservation and active site of bssSirB.

MSMHBQ_2019_v55n2_123_f0005.png 이미지

Fig. 5. Comparative structural analysis of bssSirB and its homologs.

Table 1. Crystallographic statistics of the bssSirB structure

MSMHBQ_2019_v55n2_123_t0001.png 이미지

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