1P077 NMR and docking structure of antimicrobial peptide complexed with lipopolysaccharide(01D. Protein : Function,Poster,The 52nd Annual Meeting of the Biophysical Society of Japan(BSJ2014))

Abstract

Epidemiological studies have suggested that alternating magnetic fields affect human body, but mechanism of influences on cell or human body has not established in the biological experiment yet. In order to reveal primary site of action by alternating magnetic fields, we focus on ferritin, iron-storage protein, because ferritin is source of iron ions which produce reactive oxygen species. We exposed ferritin solution to alternating magnetic fields (50Hz~500kHz for 3 h) and measured the concentration of iron ions outside ferritin. The results show that concentration of iron ions is decreased after the exposure. We are currently performing the experiment under wider conditions and will report the detailed analysis of this phenomenon. Nitrile Hydratase (NHase) catalyzes hydration of nitriles to the corresponding amides and has been used for industrial productions of various amides. The active site of NHase consists of an Fe(III) or a Co(III) ion coordinated with two carboxamido nitrogens, one cysteine-sulfer (Cys-S), one cysteine-sulfenic (Cys-SO) and one cysteine-sulfinic (Cys-SO2) moieties. Several reaction paths have been proposed for the catalytic mechanism of NHase, and recently quantum chemical calculations using active-site models were reported (Hopmann et al., 2007(Hopmann et al., , 2008(Hopmann et al., , and 2014. 1P074 ニトリルヒドラターゼ（NHase）によるアミド生成機構に関 する理論的研究In the present study, we have examined four reaction mechanisms by using Quantum Mechanics/Molecular Mechanics (QM/MM) method to reveal the effects of surrounding protein environment on the reaction process. The chaperonin GroE encapsulates a substrate in its inner cavity, assisting the folding in an ATP-dependent manner. Although the function of GroEL has been well characterized, the role of its C-terminal region remains elusive. Here, we investigated the effect of C-terminal truncation on the GroEmediated folding of GFP. We found that the yield of an in-cage folding mediated by a single-ring GroEL was significantly decreased by truncation. In contrast, the yield of an in-cage folding mediated by an ATPasedeficient double-ring GroEL, which formed a stable football shaped complex, was not affected by truncation. These results suggest that the Cterminal region of GroEL functions as a barrier between rings, preventing the leakage of GFP through the bottom space of the cage. Antimicrobial peptides (AMPs) are ubiquitously found in living organisms and has a broad antimicrobial activity against Gram-negative and Grampositive bacteria and fungi. Some AMPs can bind to lipopolysaccharide (LPS) that is a major component of the outer membrane of Gram-negative bacteria and cause fatal septic shock. Therefore, AMPs that interact with LPS are expected to be novel antibiotics for sepsis. Tachyplesin I (TP I) is one of the AMPs that binds to LPS, but complex structure between TP I and LPS and binding mechanism are still unknown. We investigated the NMR structure of TP I in the presence of LPS and determined the complex structure using docking program. It was indicat...