scholarly journals X-ray crystallographic and mass spectrometric structure determination and functional characterization of succinylated porin from rhodobacter capsulatus: Implications for ion selectivity and single-channel conductance

1996 ◽  
Vol 5 (8) ◽  
pp. 1477-1489 ◽  
Author(s):  
Michael Przybylski ◽  
Michael O. Glocker ◽  
Uwe Nestel ◽  
Volker Schnaible ◽  
Martin Blüggel ◽  
...  
Keyword(s):  
Structure Determination ◽  
Rhodobacter Capsulatus ◽  
Single Channel ◽  
Ion Selectivity ◽  
Functional Characterization ◽  
Mass Spectrometric ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
X Ray

scholarly journals Functional Characterization of VJ-gating and Single Channel Conductance of Sheep Cx46 and Cx50 Gap Junctions

2020 ◽  
Vol 118 (3) ◽  
pp. 274a
Author(s):  
Benny Yue ◽  
Bassam G. Haddad ◽  
Umair Khan ◽  
Mena Atalla ◽  
Steve L. Reichow ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Single Channel ◽  
Functional Characterization ◽  
Channel Conductance ◽  
Single Channel Conductance

Porin of Rhodobacter capsulatus: Biochemical and Functional Characterization

1990 ◽  
Vol 45 (6) ◽  
pp. 576-582 ◽  
Author(s):  
Daniela Woitzik ◽  
Jürgen Weckesser ◽  
Roland Benz ◽  
Stefan Stevanovic ◽  
Günther Jung ◽  
...  
Keyword(s):  
Gas Phase ◽  
Rhodobacter Capsulatus ◽  
Analytical Ultracentrifugation ◽  
Single Channel ◽  
Functional Characterization ◽  
Sodium Dodecyl ◽  
Single Species ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Fast Performance Liquid Chromatography

Abstract The major outer membrane protein of Rhodobacter capsulatus 37 b4 (capsule-free) was iso­lated. Strong porin-activity was observed after reconstitution into artificial lipid bilayer mem­branes with a single channel conductance of 3.15 nS in Im KC1. The porin migrated as a broad, single band (Mr above 90,000) on sodium dodecyl sulfate polyacrylamide gel electro­ phoresis and dissociated into a single species of polypeptides (Mr 36,000) on treatment with EDTA (10 mM at 30 °C, 20 min) or by heating (100 °C, 5 min). Analytical ultracentrifugation studies demonstrated the native porin to be a trimer. The monomers chromatofocused as a single, sharp peak on fast performance liquid chromatography and only one band, corre­ sponding to an isoelectric point of about 4.0, was obtained on isoelectric focusing. Gas-phase sequencing of the 23 N-terminal residues revealed Glu-Val-Lys-Leu-Ser-Gly-Asp-Ala-Arg-Met-Gly-Val-Met-Tyr-Asn-Gly-Asp-Asp-X-Asn-Phe-Ser-Ser.

Novel structural determinants of single-channel conductance in nicotinic acetylcholine and 5-hydroxytryptamine type-3 receptors

2006 ◽  
Vol 34 (5) ◽  
pp. 882-886 ◽  
Author(s):  
J.A. Peters ◽  
J.E. Carland ◽  
M.A. Cooper ◽  
M.R. Livesey ◽  
T.Z. Deeb ◽  
...  
Keyword(s):  
Transmembrane Domain ◽  
Single Channel ◽  
Ion Selectivity ◽  
Atomic Scale ◽  
Scale Model ◽  
Amino Acid Residues ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Structural Determinants ◽  
Type 3

Nicotinic ACh (acetylcholine) and 5-HT3 (5-hydroxytryptamine type-3) receptors are cation-selective ion channels of the Cys-loop transmitter-gated ion channel superfamily. Numerous lines of evidence indicate that the channel lining domain of such receptors is formed by the α-helical M2 domain (second transmembrane domain) contributed by each of five subunits present within the receptor complex. Specific amino acid residues within the M2 domain have accordingly been demonstrated to influence both single-channel conductance (γ) and ion selectivity. However, it is now clear from work performed on the homomeric 5-HT3A receptor, heteromeric 5-HT3A/5-HT3B receptor and 5-HT3A/5-HT3B receptor subunit chimaeric constructs that an additional major determinant of γ resides within a cytoplasmic domain of the receptor termed the MA-stretch (membrane-associated stretch). The MA-stretch, within the M3–M4 loop, is not traditionally thought to be implicated in ion permeation and selection. Here, we describe how such observations extend to a representative neuronal nicotinic ACh receptor composed of α4 and β2 subunits and, by inference, probably other members of the Cys-loop family. In addition, we will attempt to interpret our results within the context of a recently developed atomic scale model of the nicotinic ACh receptor of Torpedo marmorata (marbled electric ray).

scholarly journals Functional characterization of a voltage-gated anion channel from teleost fish intestinal epithelium

1988 ◽  
Vol 136 (1) ◽  
pp. 383-403 ◽  
Author(s):  
C. A. Loretz ◽  
C. R. Fourtner
Keyword(s):  
Single Channel ◽  
Basolateral Membrane ◽  
Functional Characterization ◽  
Anion Channel ◽  
Intestinal Epithelial ◽  
Channel Conductance ◽  
Patch Clamp Technique ◽  
Voltage Gated

An anion channel was isolated, using patch-clamp technique, from the basolateral membrane of goby intestinal epithelial cells. Single-channel conductance varied over a range from 20 to 90 pS. The channel was voltage-gated over the physiological range of cell membrane potential with depolarization increasing the proportion of time in the open state. There was no Ca2+ sensitivity. The selectivity sequence was SO4(2-) greater than Cl- greater than Mes-. The channel may function in vivo as one of several avenues of basolateral membrane Cl- exit with the voltage-gating property serving to match basolateral Cl- exit to apical entry.

scholarly journals A superfamily of small potassium channel subunits: form and function of the MinK-related peptides (MiRPs)

1998 ◽  
Vol 31 (4) ◽  
pp. 357-398 ◽  
Author(s):  
GEOFFREY W. ABBOTT ◽  
STEVE A. N. GOLDSTEIN
Keyword(s):  
Membrane Proteins ◽  
Ion Channel ◽  
Single Channel ◽  
Ion Selectivity ◽  
Unique Function ◽  
Type I ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Channel Function ◽  
And Function

1. INTRODUCTION 3581.1 Summary 3581.2 Overview 3591.3 Four classes of pore-forming K+channel subunits – necessary and (sometimes) sufficient 3611.4 Soluble and peripheral membrane proteins that interact with P loop subunits to alter function 3621.5 Integral membrane proteins that interact with P loop subunits to alter function 3632. MinK DETERMINES THE FUNCTION OF MIXED CHANNEL COMPLEXES 3632.1 The KCNE1 gene product (MinK) gives rise to K+-selective currents and controversy 3632.2 MinK assembles with a P loop protein, KvLQT1, to form K+channels with unique function 3642.2.1 Single-channel conductance of KvLQT1 and MinK/KvLQT1 channels 3662.2.2 Other differences between KvLQT1 and MinK/KvLQT1 channels 3672.3 MinK assembles with HERG, another P loop subunit, to regulate channel activity 3682.4 MinK does not form chloride-selective ion channels 3683. EXPERIMENTAL AND NATURAL MinK MUTATIONS 3693.1 Site-directed mutations 3693.1.1 MinK mutation alters basic channel attributes and identifies key residues 3693.1.2 MinK is a Type I transmembrane peptide 3703.1.3 MinK is intimately associated with the IKspore 3703.1.4 The number of MinK subunits in IKschannel complexes 3723.2 KCNE1 mutations associated with arrhythmia and deafness alter IKschannel function 3733.3 Summary of MinK sites critical to IKschannel function 3744. MinK-RELATED PEPTIDES: AN EMERGING SUPERFAMILY 3744.1 KCNE2, 3 and 4 encode MinK-related peptides 1, 2 and 3 (MiRPs) 3744.2 MiRP1 assembles with a P loop protein, HERG, to form K+channels with unique function 3754.2.1 MiRP1 alters activation, deactivation and single-channel conductance 3764.2.2 MiRP1 alters regulation by K+ion and confers biphasic kinetics to channel blockade 3784.2.3 Stable association of MiRP1 and HERG subunits 3804.3 KCNE2 mutations are associated with arrhythmia and decreased K+flux 3834.4 Summary of the evidence that cardiac IKrchannels are MiRP1/HERG complexes 3855. MinK-RELATED PEPTIDES: COMMONALTIES AND IMPLICATIONS 3865.1 Genetics and structure 3865.2 Cell biology and function 3876. ANSWERS, SOME OUTSTANDING ISSUES, CONCLUSIONS 3877. ACKNOWLEDGEMENTS 3898. REFERENCES 389MinK and MinK-related peptide 1 (MiRP1) are integral membrane peptides with a single transmembrane span. These peptides are active only when co-assembled with pore-forming K+ channel subunits and yet their role in normal ion channel behaviour is obligatory. In the resultant complex the peptides establish key functional attributes: gating kinetics, single-channel conductance, ion selectivity, regulation and pharmacology. Co-assembly is required to reconstitute channel behaviours like those observed in native cells. Thus, MinK/KvLQT1 and MiRP1/HERG complexes reproduce the cardiac currents called IKs and IKr, respectively. Inherited mutations in KCNE1 (encoding MinK) and KCNE2 (encoding MiRP1) are associated with lethal cardiac arrhythmias. How these mutations change ion channel behaviour has shed light on peptide structure and function. Recently, KCNE3 and KCNE4 were isolated. In this review, we consider what is known and what remains controversial about this emerging superfamily.

scholarly journals Characterization of OpdH, a Pseudomonas aeruginosa Porin Involved in the Uptake of Tricarboxylates

2006 ◽  
Vol 189 (3) ◽  
pp. 929-939 ◽  
Author(s):  
Sandeep Tamber ◽  
Elke Maier ◽  
Roland Benz ◽  
Robert E. W. Hancock
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Single Channel ◽  
Regulatory System ◽  
Growth Conditions ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Specific Expression ◽  
Large Channel ◽  
Specific Uptake

ABSTRACT The Pseudomonas aeruginosa outer membrane is intrinsically impermeable to many classes of antibiotics, due in part to its relative lack of general uptake pathways. Instead, this organism relies on a large number of substrate-specific uptake porins. Included in this group are the 19 members of the OprD family, which are involved in the uptake of a diverse array of metabolites. One of these porins, OpdH, has been implicated in the uptake of cis-aconitate. Here we demonstrate that this porin may also enable P. aeruginosa to take up other tricarboxylates. Isocitrate and citrate strongly and specifically induced the opdH gene via a mechanism involving derepression by the putative two-component regulatory system PA0756-PA0757. Planar bilayer analysis of purified OpdH demonstrated that it was a channel-forming protein with a large single-channel conductance (230 pS in 1 M KCl; 10-fold higher than that of OprD); however, we were unable to demonstrate the presence of a tricarboxylate binding site within the channel. Thus, these data suggest that the requirement for OpdH for efficient growth on tricarboxylates was likely due to the specific expression of this large-channel porin under particular growth conditions.

Sign in / Sign up

Export Citation Format

Share Document