Analysis of quaternary structure of leucine-responsive regulatory protein (Lrp) by crosslink experiments

Leucine-responsive regulatory protein (LRP) is a regulatory protein of molecular weight 18.8 kDa and is widely known to regulate many metabolic and functional activities of operons in Escherichia coli. The gene for Lrp from Escherichia coli in pQE system of 6 ${\times}$ His-tagging was expressed and $^3H$-labeled protein, as well as the wild type Lrp, was purified. The crosslink experiments were performed to analyze the quaternary structure of Lrp at high of $5{\mu}M$ and at low concentrations below $0.3{\mu}M$ with cross linkers, such as glutaraldehyde, 1, 2, 3, 4-diepoxy-butane (DEB), and ethylene glycol bis (succinimidyl succinate) (EGS). In the experiments, we found that the Lrp protein can be formed higher conformation states of tetramer, hexamer, octamer, as well as dimeric state when incubated with the above cross linkers.

교차결합 실험을 통한 루신 대응 조절 단백질의 4차 구조 분석

루신-대응 조절 단백질(Lrp)은 18.8 kDa의 분자량을 갖는 글로벌 조절 단백질로서 대장균과 같은 장내세균과에서 많은 대사작용 오페론의 기능적 활성도를 조절한다. 단백질의 4차 구조를 규명하기 위한 목적으로 Lrp단백질 코드하는 유전자가 삽입된 재조합 플라스미드 pQE vector를 발현시킨 6 ${\times}$ His-tag Lrp 야생형과 $^3H$로 표지된 Lrp를 분리 정제한 후 cross linker들인 glutaraldehyde, 1,2,3,4-diepoxy-butane (DEB), ethylene glycol bis (succinimidyl succinate) (EGS)으로 cross link 실험을 수행하여 Lrp가 $0.3{\mu}M$ 이하의 낮은 농도에서나 $5{\mu}M$의 높은 농도에서 이량체, 사량체, 육량체, 팔량체로 존재할 수 있음을 확인하였다.