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Effect of Truncation of 38 Amino Acids in N-terminal Region of ErmSF, a MLSB Antibiotic Resistance Factor Protein, on Enzymatic Activity

MLSB 항생제 내성인자인 ErmSF의 N-terminal 38개 아미노산 제거가 항생제 내성 효소활성에 미치는 영향

  • Lee, Hak Jin (Department of Bioscience and Biotechnology, College of Natural Science, The University of Suwon) ;
  • Jin, Hyung Jong (Department of Bioscience and Biotechnology, College of Natural Science, The University of Suwon)
  • 이학진 (수원대학교 자연과학대학 생명공학과) ;
  • 진형종 (수원대학교 자연과학대학 생명공학과)
  • Received : 2014.08.14
  • Accepted : 2014.09.25
  • Published : 2014.09.30

Abstract

ErmSF is one of the four antibiotic resistance factor proteins expressed by Streptomyces fradiae, antibiotic tylosin producer, which renders $MLS_B$ (macrolide-lincosamide-streptogramin B) antibiotic resistance through dimethylating A2058 of 23S rRNA, thereby reducing the affinity of antibiotic to ribosome. Unlike other Erm proteins, ErmSF harbors long N-terminal end region. To investigate its role in enzyme activity, mutant ErmSF deleted of 1-38 amino acids was overexpressed and activity in vivo and in vitro was observed. In vitro enzymatic assay showed that mutant protein exhibited reduced activity by 20% compared to the wild type enzyme. Due to the reduced activity of the mutant protein, cells expressing mutant protein showed weaker resistance to erythromycin than cells with wild type enzyme. Presumably, the decrease in enzyme activity was caused by the hindrance in substrate binding and (or) product release, not by defect in the methyl group transfer occurred in active site.

ErmSF는 macrolide 항생물질인 tylosin을 생성하는 Streptomyces fradiae가 보유한 4개의 항생제 내성인자 단백질 중 하나로 23S rRNA의 $A_{2058}$에 dimethylation 시킴으로써 항생제가 부착되는 것을 막음으로써 그 내성을 일으킨다. ErmSF는 다른 Erm 단백질과는 달리 긴 N-terminal end region을 가지고 있어서 그 역할을 알아보기 위해 1-38번째의 아미노산을 제거한 결손변이 단백질을 고안하고 대장균에서 발현하여 그 활성을 in vivo와 in vitro에서 관찰하였다. 결손변이 단백질을 발현하는 대장균은 결손에 의한 활성저하에 기인하여 야생형 단백질을 발현하는 대장균에 비하여 항생제에 대한 내성이 손상된 것을 관찰하였다. 세포 외 in vitro에서의 활성은 야생형 ErmSF에 비하여 약 20%가 손상된 것으로 나타났다. 이렇게 관찰된 활성의 저하는 결손 변이에 의한 활성화 부위에서 일어난 결손에 의한 것이라기 보다는 기질의 부착 또는 생성물의 효소에서의 이탈 과정이 손상되어서 나타나는 것으로 사료된다.

Keywords

References

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