Correlation between the OmpG Secondary Structure and Its pH-Dependent Alterations Monitored by FTIR

Korkmaz-Özkan, Filiz; Köster, Stefan; Kühlbrandt, Werner; Mäntele, Werner; Yıldız, Özkan

doi:10.1016/j.jmb.2010.06.015

Cited by 26 publications

(26 citation statements)

References 39 publications

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“…14a ). An interesting picture is obtained when superimposing all available X-ray structures 7 , 8 , 10 , 27 , 28 4CTD (loop 6 deletion), 2IWW, 2IWV, 2P1C, 2X9K, 2WVP (cysteine mutant synthetically modified). In this superposition, loops 3, 4, and 5 adopt very similar positions, and loops 1, 2, 6, and 7 diverge considerably, although much less so than in the NMR structures (Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

Structure of outer membrane protein G in lipid bilayers

et al. 2017

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β-barrel proteins mediate nutrient uptake in bacteria and serve vital functions in cell signaling and adhesion. For the 14-strand outer membrane protein G of Escherichia coli, opening and closing is pH-dependent. Different roles of the extracellular loops in this process were proposed, and X-ray and solution NMR studies were divergent. Here, we report the structure of outer membrane protein G investigated in bilayers of E. coli lipid extracts by magic-angle-spinning NMR. In total, 1847 inter-residue 1H–1H and 13C–13C distance restraints, 256 torsion angles, but no hydrogen bond restraints are used to calculate the structure. The length of β-strands is found to vary beyond the membrane boundary, with strands 6–8 being the longest and the extracellular loops 3 and 4 well ordered. The site of barrel closure at strands 1 and 14 is more disordered than most remaining strands, with the flexibility decreasing toward loops 3 and 4. Loop 4 presents a well-defined helix.

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Section: Resultsmentioning

confidence: 99%

Structure of outer membrane protein G in lipid bilayers

et al. 2017

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“…85 In this study, FTIR spectroscopy is used to investigate the struc-86 tural and functional properties of OmpG-16S. The results are com-87 pared with the results previously obtained for OmpG-WT [6,7]. 88 FTIR spectroscopy provides direct information on bond orders, The protein purity and refolding is monitored by SDS-PAGE.…”

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confidence: 66%

“…88 FTIR spectroscopy provides direct information on bond orders, The protein purity and refolding is monitored by SDS-PAGE. 130 Afterwards the buffer is exchanged to 25 mM Tris-HCl pH 8.0 con-131 taining 0.5% OG and the pure protein (>95%) is concentrated to 132 10 mg/ml by ultrafiltration (Centricon is 68% and at neutral pH is 71% as shown in the X-ray structure [4] 215 and as also confirmed by IR-spectroscopy [6,7]. A detailed analysis 216 of the Amide I band of OmpG-WT showed that the b-sheet signal 217 is shifted to lower wavenumbers at neutral pH compared to the 218 same signal at acidic pH.…”

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confidence: 94%

“…It is a nonspecific, monomeric porin for 45 the passage of ions and molecules up to 900 Da [1][2][3]. OmpG has 46 been extensively studied using many techniques like X-ray crystal-47 lography [4], single molecule force spectroscopy [5], atomic force 48 microscopy [3] and FTIR spectroscopy [6,7]. In these studies, the 49 details of its structure in various conditions have been revealed.…”

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confidence: 99%

“…At acidic pH, the imidazole ring 57 of these histidines are protonated and repel each other, which 58 causes the bending of loop L6 that connects b-strand S11-S12 into 59 the channel to block it. At neutral pH, both histidines are deproto- role of histidines in opening/closing the channel was shown by 65 mutating both histidines to alanines and cysteines [6]. It was also 66 shown that the opening/closing is driven by the formation/break-67 ing of hydrogen bridges in b-strands S11-S13 as well as by the 68 electrostatic interactions among positive and negatively charged 69 side chains [7].…”

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IR-spectroscopic characterization of an elongated OmpG mutant

Korkmaz

Pee

Yıldız

2015

Archives of Biochemistry and Biophysics

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Strategies and Perspectives in Ion‐Channel Engineering

2011

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Membranes form natural barriers that need to be permeable to diverse matter like ions and substrates. This permeability is controlled by ion-channel proteins, which have attracted great interest for pharmaceutical applications. Ion-channel engineering (ICE) modifies biological ion channels by chemical/biological synthetis means. The goal is to obtain ion channels with modified or novel functionality. Three functional strategies exist. The first is the manipulation of the wider pores with robust β-barrel structures, such as those of α-hemolysin and porins. The second engineering approach focuses on the modification of narrow (mostly α-helical) pores to understand selectivity and modes of action. A third functional approach addresses channel gating by (photo)triggering the biological receptor that controls the channel. Several synthetis strategies have been developed and successfully utilized for the synthetic modification of biological ion-channels: the S-alkylation of specifically introduced Cys, protein semisynthesis by native chemical ligation, protein semisynthesis by protein trans-splicing, as well as nonsense-suppression methods. Structural studies (X-ray crystallography, NMR spectroscopy) are necessary to support the functional studies and to afford predictable engineering. The reprogramming and re-engineering of channels can be used for sensing applications, treatment of channelopathies, chemical neurobiology, and providing novel lead compounds for targeting ion channels.

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Correlation between the OmpG Secondary Structure and Its pH-Dependent Alterations Monitored by FTIR

Cited by 26 publications

References 39 publications

Structure of outer membrane protein G in lipid bilayers

Structure of outer membrane protein G in lipid bilayers

IR-spectroscopic characterization of an elongated OmpG mutant

Strategies and Perspectives in Ion‐Channel Engineering

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