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토마토 (Solanum lycopersicum) 과육의 숙성정도에 따른 peptide:N-glycanase 발현 분석

Characterization of peptide:N-glycanase from tomato (Solanum lycopersicum) fruits

  • 위수진 (순천대학교 생명산업과학대학 생물학과) ;
  • 박기영 (순천대학교 생명산업과학대학 생물학과)
  • Wi, Soo Jin (Department of Biology, Sunchon National University) ;
  • Park, Ky Young (Department of Biology, Sunchon National University)
  • 투고 : 2014.09.11
  • 심사 : 2014.09.15
  • 발행 : 2014.09.30

초록

진핵생물의 유전자 발현 과정에서 생성된 단백질은 전사후 변형 과정을 통해 소포체와 골지체에서 당질화가 일어난다. 당질화된 당단백질은 접힘의 오류가 있는 경우를 비롯하여 식물의 분화 조절 등의 경우 당단백질이 분해되며, 이 때 PNGase에 의해 N-당사슬이 단백질의 아스파라긴산 잔기로부터 절단된다. 그러나 식물의 발달과 분화 과정에서 PNGase의 발현 조절에 대해서는 거의 알려진 바가 없다. 기존에 보고된 유전적 정보를 활용하여 토마토의 잎에서 제조된 cDNA library에서 nested RT-PCR을 통하여 PNGase T의 유전자(GenBank Accession number KM401550)를 분리하였는데 이의 ORF는 1,767 bp, 588개의 이미노산으로 이루어졌으며, 분자량은 65.8 KDa이었다. PNGase T의 유전자는 토마토 과육에서 높은 수준으로 항시적으로 발현되었으며, 특히 녹색과보다는 오렌지색으로 숙성되는 과정에서 PNGase T의 전사체량이 크게 증가하였다. 이러한 발현 패턴은 토마토 과육에서 세포죽음의 과정에서 증가하는 단백질 가수분해 효소인 metacaspase의 전사체 증가 페턴과 유사하였으며, 이 시기에는 에틸렌의 생합성 효소 중 노화관련 ACC synthase의 유전자 members (LeACS2, LeACS4, LeACS6)의 발현 패턴과도 유사하였다. 따라서 토마토 과육에서 PNGase T의 유전자 발현은 거대분자가 분해되는 시기에서 과육의 숙성과 노화 과정에서 특이적인 생리적 기능을 나타내는 것으로 판단된다. 향 후 고가의 의약용 재조합단백질의 면역부작용을 완화하기 위하여 식물체 유래의 당단백질의 탈당질화과정에서 PNGase T를 활용함으로써 식물생명공학 분야에서 활용가치가 높을 것으로 사료된다.

In eukaryotes, proteins that are secreted into ER are post-translationally modified by N-glycosylation, the patterns of which are significantly different between plant and animal cells. Biotechnology industry has already produced a number of therapeutic glycoproteins in plant cells. However, the aberrant glycosylation of therapeutic recombinant proteins in plant systems can cause immune problems in humans. Therefore, it is important to develop strategies for producing non-glycosylated forms to preserve biological activity and native conformation by a peptide: N-glycanase (PNGase). In this study, we try to isolate PNGase T gene from tomato, which can use as a platform plant for biotechnology industry. We isolated a cDNA (GenBank Accession number KM401550) from tomato leaves with 1,767 bp, which encoded a polypeptide of 588 amino acids with a predicted molecular mass of 65.8 kDa. We also investigated the expression patterns of PNGase T during fruit ripening of tomato. The transcripts of PNGase T, which were constitutively induced in tomato fruit from green stage, were significantly increased and reached a peak at orange stage. After which, those transcripts were continuously reduced. The expression pattern of PNGase T was coincided well with transcripts profiles of metacaspase gene, LeMCA, and senescence-related gene members of ACC synthase, LeACS2, LeACS4, and LeACS6, for ethylene biosynthesis during fruit ripening. These results suggest that PNGase T is involved in a de-glycosylation process associated with senescence and fruit ripening.

키워드

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