1
|
Bhattacharya A, Falk ID, Moss FR, Weiss TM, Tran KN, Burns NZ, Boxer SG. Structure-function relationships in pure archaeal bipolar tetraether lipids. Chem Sci 2024:d4sc03788j. [PMID: 39149219 PMCID: PMC11320390 DOI: 10.1039/d4sc03788j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2024] [Accepted: 08/05/2024] [Indexed: 08/17/2024] Open
Abstract
Archaeal bipolar tetraether lipids (BTLs) are among the most unusual lipids occurring in nature because of their presumed ability to span the entire membrane to form a monolayer structure. It is believed that because of their unique structural organization and chemical stability, BTLs offer extraordinary adaptation to archaea to thrive in the most extreme milieus. BTLs have also received considerable attention for development of novel membrane-based materials. Despite their fundamental biological significance and biotechnological interests, prior studies on pure BTLs are limited because of the difficulty to extract them in pure form from natural sources or to synthesize them chemically. Here we have utilized chemical synthesis to enable in-depth biophysical investigations on a series of chemically pure glycerol dialkyl glycerol tetraether (GDGT) lipids. The lipids self-assemble to form membrane-bound vesicles encapsulating polar molecules in aqueous media, and reconstitute a functional integral membrane protein. Structural properties of the membranes were characterized via small-angle X-ray scattering (SAXS) and cryogenic electron microscopy (cryo-EM). SAXS studies on bulk aqueous dispersions of GDGT lipids over 10-90 °C revealed lamellar and non-lamellar phases and their transitions. Next we asked whether vesicles overwhelmingly composed of a single GDGT species can undergo fusion as it is difficult to conceptualize such behavior with the assumption that such membranes have a monolayer structure. Interestingly, we observed that GDGT vesicles undergo fusion with influenza virus with lipid mixing kinetics comparable to that with vesicles composed of monopolar phospholipids. Our results suggest that GDGT membranes may consist of regions with a bilayer structure or form bilayer structures transiently which facilitate fusion and thus offer insight into how archaea may perform important physiological functions that require dynamical membrane behavior.
Collapse
Affiliation(s)
- Ahanjit Bhattacharya
- Department of Chemistry, Stanford University Stanford CA 94305 USA
- Stanford Center for Innovation in Global Health, Stanford University Stanford CA 94305 USA
| | - Isaac D Falk
- Department of Chemistry, Stanford University Stanford CA 94305 USA
| | - Frank R Moss
- Linac Coherent Light Source, SLAC National Accelerator Laboratory Menlo Park CA 94025 USA
| | - Thomas M Weiss
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory Menlo Park CA 94025 USA
| | - Khoi N Tran
- Department of Chemistry, Stanford University Stanford CA 94305 USA
| | - Noah Z Burns
- Department of Chemistry, Stanford University Stanford CA 94305 USA
| | - Steven G Boxer
- Department of Chemistry, Stanford University Stanford CA 94305 USA
| |
Collapse
|
2
|
Lipopeptides in promoting signals at surface/interface of micelles: Their roles in repairing cellular and nuclear damages. FOOD BIOSCI 2022. [DOI: 10.1016/j.fbio.2021.101522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
3
|
Certain, but Not All, Tetraether Lipids from the Thermoacidophilic Archaeon Sulfolobus acidocaldarius Can Form Black Lipid Membranes with Remarkable Stability and Exhibiting Mthk Channel Activity with Unusually High Ca 2+ Sensitivity. Int J Mol Sci 2021; 22:ijms222312941. [PMID: 34884746 PMCID: PMC8657495 DOI: 10.3390/ijms222312941] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 11/25/2021] [Accepted: 11/27/2021] [Indexed: 11/19/2022] Open
Abstract
Bipolar tetraether lipids (BTL) have been long thought to play a critical role in allowing thermoacidophiles to thrive under extreme conditions. In the present study, we demonstrated that not all BTLs from the thermoacidophilic archaeon Sulfolobus acidocaldarius exhibit the same membrane behaviors. We found that free-standing planar membranes (i.e., black lipid membranes, BLM) made of the polar lipid fraction E (PLFE) isolated from S. acidocaldarius formed over a pinhole on a cellulose acetate partition in a dual-chamber Teflon device exhibited remarkable stability showing a virtually constant capacitance (~28 pF) for at least 11 days. PLFE contains exclusively tetraethers. The dominating hydrophobic core of PLFE lipids is glycerol dialky calditol tetraether (GDNT, ~90%), whereas glycerol dialkyl glycerol tetraether (GDGT) is a minor component (~10%). In sharp contrast, BLM made of BTL extracted from microvesicles (Sa-MVs) released from the same cells exhibited a capacitance between 36 and 39 pF lasting for only 8 h before membrane dielectric breakdown. Lipids in Sa-MVs are also exclusively tetraethers; however, the dominating lipid species in Sa-MVs is GDGT (>99%), not GDNT. The remarkable stability of BLMPLFE can be attributed to strong PLFE–PLFE and PLFE–substrate interactions. In addition, we compare voltage-dependent channel activity of calcium-gated potassium channels (MthK) in BLMPLFE to values recorded in BLMSa-MV. MthK is an ion channel isolated from a methanogenic that has been extensively characterized in diester lipid membranes and has been used as a model for calcium-gated potassium channels. We found that MthK can insert into BLMPLFE and exhibit channel activity, but not in BLMSa-MV. Additionally, the opening/closing of the MthK in BLMPLFE is detectable at calcium concentrations as low as 0.1 mM; conversely, in diester lipid membranes at such a low calcium concentration, no MthK channel activity is detectable. The differential effect of membrane stability and MthK channel activity between BLMPLFE and BLMSa-MV may be attributed to their lipid structural differences and thus their abilities to interact with the substrate and membrane protein. Since Sa-MVs that bud off from the plasma membrane are exclusively tetraether lipids but do not contain the main tetraether lipid component GDNT of the plasma membrane, domain segregation must occur in S. acidocaldarius. The implication of this study is that lipid domain formation is existent and functionally essential in all kinds of cells, but domain formation may be even more prevalent and pronounced in hyperthermophiles, as strong domain formation with distinct membrane behaviors is necessary to counteract randomization due to high growth temperatures while BTL in general make archaea cell membranes stable in high temperature and low pH environments whereas different BTL domains play different functional roles.
Collapse
|
4
|
Straub CT, Counts JA, Nguyen DMN, Wu CH, Zeldes BM, Crosby JR, Conway JM, Otten JK, Lipscomb GL, Schut GJ, Adams MWW, Kelly RM. Biotechnology of extremely thermophilic archaea. FEMS Microbiol Rev 2018; 42:543-578. [PMID: 29945179 DOI: 10.1093/femsre/fuy012] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Accepted: 06/23/2018] [Indexed: 12/26/2022] Open
Abstract
Although the extremely thermophilic archaea (Topt ≥ 70°C) may be the most primitive extant forms of life, they have been studied to a limited extent relative to mesophilic microorganisms. Many of these organisms have unique biochemical and physiological characteristics with important biotechnological implications. These include methanogens that generate methane, fermentative anaerobes that produce hydrogen gas with high efficiency, and acidophiles that can mobilize base, precious and strategic metals from mineral ores. Extremely thermophilic archaea have also been a valuable source of thermoactive, thermostable biocatalysts, but their use as cellular systems has been limited because of the general lack of facile genetics tools. This situation has changed recently, however, thereby providing an important avenue for understanding their metabolic and physiological details and also opening up opportunities for metabolic engineering efforts. Along these lines, extremely thermophilic archaea have recently been engineered to produce a variety of alcohols and industrial chemicals, in some cases incorporating CO2 into the final product. There are barriers and challenges to these organisms reaching their full potential as industrial microorganisms but, if these can be overcome, a new dimension for biotechnology will be forthcoming that strategically exploits biology at high temperatures.
Collapse
Affiliation(s)
- Christopher T Straub
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - James A Counts
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Diep M N Nguyen
- Department of Biochemistry and Molecular Biology University of Georgia, Athens, GA 30602, USA
| | - Chang-Hao Wu
- Department of Biochemistry and Molecular Biology University of Georgia, Athens, GA 30602, USA
| | - Benjamin M Zeldes
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - James R Crosby
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Jonathan M Conway
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Jonathan K Otten
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Gina L Lipscomb
- Department of Biochemistry and Molecular Biology University of Georgia, Athens, GA 30602, USA
| | - Gerrit J Schut
- Department of Biochemistry and Molecular Biology University of Georgia, Athens, GA 30602, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology University of Georgia, Athens, GA 30602, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695-7905, USA
| |
Collapse
|
5
|
Šuštar V, Zelko J, Lopalco P, Lobasso S, Ota A, Ulrih NP, Corcelli A, Kralj-Iglič V. Morphology, biophysical properties and protein-mediated fusion of archaeosomes. PLoS One 2012; 7:e39401. [PMID: 22792173 PMCID: PMC3391208 DOI: 10.1371/journal.pone.0039401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 05/22/2012] [Indexed: 12/22/2022] Open
Abstract
As variance from standard phospholipids of eubacteria and eukaryotes, archaebacterial diether phospholipids contain branched alcohol chains (phytanol) linked to glycerol exclusively with ether bonds. Giant vesicles (GVs) constituted of different species of archaebacterial diether phospholipids and glycolipids (archaeosomes) were prepared by electroformation and observed under a phase contrast and/or fluorescence microscope. Archaebacterial lipids and different mixtures of archaebacterial and standard lipids formed GVs which were analysed for size, yield and ability to adhere to each other due to the mediating effects of certain plasma proteins. GVs constituted of different proportions of archaeal or standard phosphatidylcholine were compared. In nonarchaebacterial GVs (in form of multilamellar lipid vesicles, MLVs) the main transition was detected at Tm = 34. 2°C with an enthalpy of ΔH = 0.68 kcal/mol, whereas in archaebacterial GVs (MLVs) we did not observe the main phase transition in the range between 10 and 70°C. GVs constituted of archaebacterial lipids were subject to attractive interaction mediated by beta 2 glycoprotein I and by heparin. The adhesion constant of beta 2 glycoprotein I – mediated adhesion determined from adhesion angle between adhered GVs was in the range of 10−8 J/m2. In the course of protein mediated adhesion, lateral segregation of the membrane components and presence of thin tubular membranous structures were observed. The ability of archaebacterial diether lipids to combine with standard lipids in bilayers and their compatibility with adhesion-mediating molecules offer further evidence that archaebacterial lipids are appropriate for the design of drug carriers.
Collapse
Affiliation(s)
- Vid Šuštar
- Laboratory of Clinical Biophysics, Chair of Orthopaedics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Jasna Zelko
- Laboratory of Clinical Biophysics, Chair of Orthopaedics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Patrizia Lopalco
- Department of Medical Biochemistry, Biology and Physics, University of Bari Aldo Moro, Bari, Italy
| | - Simona Lobasso
- Department of Medical Biochemistry, Biology and Physics, University of Bari Aldo Moro, Bari, Italy
| | - Ajda Ota
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Nataša Poklar Ulrih
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Angela Corcelli
- Department of Medical Biochemistry, Biology and Physics, University of Bari Aldo Moro, Bari, Italy
- IPCF-CNR, Bari, Italy
| | - Veronika Kralj-Iglič
- Biomedical Research Group, Faculty of Health Sciences, University of Ljubljana, Ljubljana, Slovenia
- * E-mail:
| |
Collapse
|
6
|
Jeworrek C, Evers F, Erlkamp M, Grobelny S, Tolan M, Chong PLG, Winter R. Structure and phase behavior of archaeal lipid monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13113-13121. [PMID: 21910469 DOI: 10.1021/la202027s] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report X-ray reflectivity (XRR) and grazing incidence X-ray diffraction (GIXD) measurements of archaeal bipolar tetraether lipid monolayers at the air-water interface. Specifically, Langmuir films made of the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius grown at three different temperatures, i.e., 68, 76, and 81 °C, were examined. The dependence of the structure and packing properties of PLFE monolayers on surface pressure were analyzed in a temperature range between 10 and 50 °C at different pH values. Additionally, the interaction of PLFE monolayers (using lipids derived from cells grown at 76 °C) with the ion channel peptide gramicidin was investigated as a function of surface pressure. A total monolayer thickness of approximately 30 Å was found for all monolayers, hinting at a U-shaped conformation of the molecules with both head groups in contact with the interface. The monolayer thickness increased with rising film pressure and decreased with increasing temperature. At 10 and 20 °C, large, highly crystalline domains were observed by GIXD, whereas at higher temperatures no distinct crystallinity could be observed. For lipids derived from cells grown at higher temperatures, a slightly more rigid structure in the lipid dibiphytanyl chains was observed. A change in the pH of the subphase had an influence only on the structure of the lipid head groups. The addition of gramicidin to an PLFE monolayer led to a more disordered state as observed by XRR. In GIXD measurements, no major changes in lateral organization could be observed, except for a decrease of the size of crystalline domains, indicating that gramicidin resides mainly in the disordered areas of the monolayer and causes local membrane perturbation, only.
Collapse
Affiliation(s)
- Christoph Jeworrek
- Physical Chemistry I, Faculty of Chemistry, TU Dortmund University, Dortmund, Otto-Hahn-Strasse 6, D-44221 Dortmund, Germany
| | | | | | | | | | | | | |
Collapse
|
7
|
Chong PLG, Sulc M, Winter R. Compressibilities and volume fluctuations of archaeal tetraether liposomes. Biophys J 2010; 99:3319-26. [PMID: 21081080 PMCID: PMC2980700 DOI: 10.1016/j.bpj.2010.09.061] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 09/29/2010] [Accepted: 09/30/2010] [Indexed: 11/16/2022] Open
Abstract
Bipolar tetraether lipids (BTLs) are abundant in crenarchaeota, which thrive in both thermophilic and nonthermophilic environments, with wide-ranging growth temperatures (4-108°C). BTL liposomes can serve as membrane models to explore the role of BTLs in the thermal stability of the plasma membrane of crenarchaeota. In this study, we focus on the liposomes made of the polar lipid fraction E (PLFE). PLFE is one of the main BTLs isolated from the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. Using molecular acoustics (ultrasound velocimetry and densimetry), pressure perturbation calorimetry, and differential scanning calorimetry, we have determined partial specific adiabatic and isothermal compressibility, their respective compressibility coefficients, partial specific volume, and relative volume fluctuations of PLFE large unilamellar vesicles (LUVs) over a wide range of temperatures (20-85°C). The results are compared with those obtained from liposomes made of dipalmitoyl-L-α-phosphatidylcholine (DPPC), a conventional monopolar diester lipid. We found that, in the entire temperature range examined, compressibilities of PLFE LUVs are low, comparable to those found in gel state of DPPC. Relative volume fluctuations of PLFE LUVs at any given temperature examined are 1.6-2.2 times more damped than those found in DPPC LUVs. Both compressibilities and relative volume fluctuations in PLFE LUVs are much less temperature-sensitive than those in DPPC liposomes. The isothermal compressibility coefficient (β(T)(lipid)) of PLFE LUVs changes from 3.59 × 10(-10) Pa(-1) at 25°C to 4.08 × 10(-10) Pa(-1) at 78°C. Volume fluctuations of PLFE LUVs change only 0.25% from 30°C to 80°C. The highly damped volume fluctuations and their low temperature sensitivity, echo that PLFE liposomes are rigid and tightly packed. To our knowledge, the data provide a deeper understanding of lipid packing in PLFE liposomes than has been previously reported, as well as a molecular explanation for the low solute permeation and limited membrane lateral motion. The obtained results may help to establish new strategies for rational design of stable BTL-based liposomes for drug/vaccine delivery.
Collapse
Affiliation(s)
- Parkson Lee-Gau Chong
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania
| | - Michael Sulc
- Faculty of Chemistry, Physical Chemistry I, Biophysical Chemistry, Technical University of Dortmund, Dortmund, Germany
| | - Roland Winter
- Faculty of Chemistry, Physical Chemistry I, Biophysical Chemistry, Technical University of Dortmund, Dortmund, Germany
| |
Collapse
|
8
|
Chong PLG. Archaebacterial bipolar tetraether lipids: Physico-chemical and membrane properties. Chem Phys Lipids 2010; 163:253-65. [PMID: 20060818 DOI: 10.1016/j.chemphyslip.2009.12.006] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 12/18/2009] [Accepted: 12/30/2009] [Indexed: 11/18/2022]
Abstract
Bipolar tetraether lipids (BTL) are abundant in archaea and can be chemically synthesized. The structures of BTL are distinctly different from the lipids found in bacteria and eukaryotes. In aqueous solution, BTL can form extraordinarily stable liposomes with different sizes, lamellarities and membrane packing densities. BTL liposomes can serve as membrane models for understanding the structure-function relationship of the plasma membrane in thermoacidophiles and can be used for technological applications. This article reviews the separation, characterization and structures of BTL as well as the physical properties and technological applications of BTL liposomes. One of the structural features of BTL is the presence of cyclopentane rings in the lipid hydrocarbon core. Archaea use the cyclopentane ring as an adaptation strategy to cope with high growth temperature. Special attention of this article is focused on how the number of cyclopentane rings varies with environmental factors and affects membrane properties.
Collapse
Affiliation(s)
- Parkson Lee-Gau Chong
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, United States.
| |
Collapse
|
9
|
Abstract
Archaea have developed specific tools permitting life under harsh conditions and archaeal lipids are one of these tools. This microreview describes the particular features of tetraether-type archaeal lipids and their potential applications in biotechnology. Natural and synthetic tetraether lipid structures as well as their applications in drug/gene delivery, vaccines and proteoliposomes or as lipid films are reviewed.
Collapse
|
10
|
|
11
|
Chong PLG, Ravindra R, Khurana M, English V, Winter R. Pressure perturbation and differential scanning calorimetric studies of bipolar tetraether liposomes derived from the thermoacidophilic archaeon Sulfolobus acidocaldarius. Biophys J 2005; 89:1841-9. [PMID: 15980181 PMCID: PMC1366687 DOI: 10.1529/biophysj.105.063933] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 06/17/2005] [Indexed: 11/18/2022] Open
Abstract
Differential scanning calorimetry (DSC) and pressure perturbation calorimetry (PPC) were used to characterize thermal phase transitions, membrane packing, and volumetric properties in multilamellar vesicles (MLVs) composed of the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius grown at different temperatures. For PLFE MLVs derived from cells grown at 78 degrees C, the first DSC heating scan exhibits an endothermic transition at 46.7 degrees C, a small hump near 60 degrees C, and a broad exothermic transition at 78.5 degrees C, whereas the PPC scan reveals two transitions at approximately 45 degrees C and 60 degrees C. The endothermic peak at 46.7 degrees C is attributed to a lamellar-to-lamellar phase transition and has an unusually low DeltaH (3.5 kJ/mol) and DeltaV/V (0.1%) value, as compared to those for the main phase transitions of saturated diacyl monopolar diester lipids. This result may arise from the restricted trans-gauche conformational changes in the dibiphytanyl chain due to the presence of cyclopentane rings and branched methyl groups and due to the spanning of the lipid molecules over the whole membrane. The exothermic peak at 78.5 degrees C probably corresponds to a lamellar-to-cubic phase transition and exhibits a large and negative DeltaH value (-23.2 kJ/mol), which is uncommon for normal lamellar-to-cubic phospholipid phase transformations. This exothermic transition disappears in the subsequent heating scans and thus may involve a metastable phase, which is irreversible at the scan rate used. Further, there is no distinct peak in the plot of the thermal expansion coefficient alpha versus temperature near 78.5 degrees C, indicating that this lamellar-to-cubic phase transition is not accompanied by any significant volume change. For PLFE MLVs derived from cells grown at 65 degrees C, similar DSC and PPC profiles and thermal history responses were obtained. However, the lower growth temperature yields a higher DeltaV/V ( approximately 0.25%) and DeltaH (14 kJ/mol) value for the lamellar-to-lamellar phase transition measured at the same pH (2.1). A lower growth temperature also generates a less negative temperature dependence of alpha. The changes in DeltaV/V, DeltaH, and the temperature dependence of alpha can be attributed to the decrease in the number of cyclopentane rings in PLFE at the lower growth temperature. The relatively low DeltaV/V and small DeltaH involved in the phase transitions help to explain why PLFE liposomes are remarkably thermally stable and also echo the proposal that PLFE liposomes are generally rigid and tightly packed. These results help us to understand why, despite the occurrence of thermal-induced phase transitions, PLFE liposomes exhibit a remarkably low temperature sensitivity of proton permeation and dye leakage.
Collapse
Affiliation(s)
- Parkson Lee-Gau Chong
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
| | | | | | | | | |
Collapse
|
12
|
Muntyan MS, Popova IV, Bloch DA, Skripnikova EV, Ustiyan VS. Energetics of alkalophilic representatives of the genus Bacillus. BIOCHEMISTRY (MOSCOW) 2005; 70:137-42. [PMID: 15807650 DOI: 10.1007/s10541-005-0092-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Cytochrome and lipid composition of membranes is considered as the attributes required for adaptation of the alkalophiles to alkaline conditions. Respiratory chains of alkalophilic representatives of the genus Bacillus are discussed. Special attention is paid to the features of the Na(+)-cycle of these bacteria and to the features determining halo- and alkalotolerant phenotype, which have been reported due to recent achievements in genomics.
Collapse
Affiliation(s)
- M S Muntyan
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia.
| | | | | | | | | |
Collapse
|
13
|
Structure and permeability properties of biomimetic membranes of bolaform archaeal tetraether lipids. J Memb Sci 2002. [DOI: 10.1016/s0376-7388(01)00771-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
14
|
Abstract
Bacterial and archaeal complete genome sequences have been obtained from a wide range of evolutionary lines, which allows some general conclusions about the phylogenetic distribution and evolution of bioenergetic pathways to be drawn. In particular, I searched in the complete genomes for key enzymes involved in aerobic and anaerobic respiratory pathways and in photosynthesis, and mapped them into an rRNA tree of sequenced species. The phylogenetic distribution of these enzymes is very irregular, and clearly shows the diverse strategies of energy conservation used by prokaryotes. In addition, a thorough phylogenetic analysis of other bioenergetic protein families of wide distribution reveals a complex evolutionary history for the respective genes. A parsimonious explanation for these complex phylogenetic patterns and for the irregular distribution of metabolic pathways is that the last common ancestor of Bacteria and Archaea contained several members of every gene family as a consequence of previous gene or genome duplications, while different patterns of gene loss occurred during the evolution of every gene family. This would imply that the last universal ancestor was a bioenergetically sophisticated organism. Finally, important steps that occurred during the evolution of energetic machineries, such as the early evolution of aerobic respiration and the acquisition of eukaryotic mitochondria from a proteobacterium ancestor, are supported by the analysis of the complete genome sequences.
Collapse
Affiliation(s)
- J Castresana
- European Molecular Biology Laboratory, Biocomputing Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
| |
Collapse
|
15
|
Bagatolli L, Gratton E, Khan TK, Chong PL. Two-photon fluorescence microscopy studies of bipolar tetraether giant liposomes from thermoacidophilic archaebacteria Sulfolobus acidocaldarius. Biophys J 2000; 79:416-25. [PMID: 10866967 PMCID: PMC1300945 DOI: 10.1016/s0006-3495(00)76303-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The effects of temperature and pH on Laurdan (6-lauroyl-2-(dimethylamino)naphthalene) fluorescence intensity images of giant unilamellar vesicles (GUVs) ( approximately 20-150 microm in diameter) composed of the polar lipid fraction E (PLFE) from the thermoacidophilic archaebacteria Sulfolobus acidocaldarius have been studied using two-photon excitation. PLFE GUVs made by the electroformation method were stable and well suited for microscopy studies. The generalized polarization (GP) of Laurdan fluorescence in the center cross section of the vesicles has been determined as a function of temperature at pH 7.23 and pH 2.68. At all of the temperatures and pHs examined, the GP values are low (below or close to 0), and the GP histograms show a broad distribution width (> 0.3). When excited with light polarized in the y direction, Laurdan fluorescence in the center cross section of the PLFE GUVs exhibits a photoselection effect showing much higher intensities in the x direction of the vesicles, a result opposite that previously obtained on monopolar diester phospholipids. This result indicates that the chromophore of Laurdan in PLFE GUVs is aligned parallel to the membrane surface. The x direction photoselection effect and the low GP values lead us to further propose that the Laurdan chromophore resides in the polar headgroup region of the PLFE liposomes, while the lauroyl tail inserts into the hydrocarbon core of the membrane. This unusual L-shaped disposition is presumably caused by the unique lipid structures and by the rigid and tight membrane packing in PLFE liposomes. The GP exhibited, at both pH values, a small but abrupt decrease near 50 degrees C, suggesting a conformational change in the polar headgroups of PLFE. This transition temperature fully agrees with the d-spacing data recently measured by small-angle x-ray diffraction and with the pyrene-labeled phosphatidylcholine and perylene fluorescence data previously obtained from PLFE multilamellar vesicles. Interestingly, the two-photon Laurdan fluorescence images showed snowflake-like lipid domains in PLFE GUVs at pH 7.23 and low temperatures (<20 degrees C in the cooling scan and <24 degrees C in the heating scan). These domains, attributable to lipid lateral separation, were stable and laterally immobile at low temperatures (<23 degrees C), again suggesting tight membrane packing in the PLFE GUVs.
Collapse
Affiliation(s)
- L Bagatolli
- Laboratory for Fluorescence Dynamics, Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | | | | |
Collapse
|
16
|
Abstract
Membranes composed of glycerol dialkylnonitol tetraether (GDNT) lipids from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius have been studied by molecular modeling. GDNT membranes containing eight cyclopentane rings in the molecule are packed much tighter than those without rings. When containing eight cyclopentane rings, the beta-D-galactosyl-D-glucose head-group of GDNT runs almost parallel to the membrane surface. However, when containing no rings, the head-group is oriented perpendicular to the membrane surface. Using molecular dynamics calculations, we have also conducted comparative studies of membrane packing between GDNT and various non-archaebacterial membranes. Compared to gel state dipalmitoylphosphatidylcholine (DPPC) and gel state distearoylphosphatidylcholine (DSPC) bilayers, the GDNT membrane with eight cyclopentane rings has a more negative interaction energy, thus a tighter membrane packing, while the GDNT without rings is less tightly packed than gel state DSPC. Based on the calculated interaction energies, the GDNT membranes (with and without rings) are much more tightly packed than DPhPC (an ester-linked diphytanyl PC) and DPhyPC (an ether-linked diphytanyl PC) bilayers. This suggests that the branched methyl group in the phytanyl chain is not the major contributor of the tight packing of GDNT membranes. The biological implication of this study is that the cyclopentane ring could increase GDNT membrane thermal stability. This explains why the number of cyclopentane rings in archaebacterial lipid increases with increasing growth temperature. Perhaps, through the ring-temperature compensation mechanism the plasma membrane of thermoacidophilic archaebacteria is able to maintain a tight and rigid structure, consequently, a constant proton gradient between the extracellular (pH 2.5) and intracellular compartment (pH 6.5), over a wide range of growth temperatures.
Collapse
Affiliation(s)
- J L Gabriel
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | | |
Collapse
|
17
|
Abstract
Membrane packing and dynamics of bipolar tetraether liposomes composed of the polar lipid fraction E (PLFE) from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius have been studied by perylene fluorescence. At a probe-to-PLFE lipid ratio of 1:400, we have detected an unusual fluorescence intensity increase with increasing temperature, while the fluorescence lifetime changed little. As the ratio was decreased, the intensity anomaly was diminished. At 1:3200 and 1:6400, the anomaly disappeared. A remarkable perylene intensity anomaly was also observed in bilayers composed of saturated monopolar diester phosphatidylcholines at their main phase transition temperatures. These results suggest that the intensity anomaly may be due to probe aggregation caused by tight membrane packing. At the same probe-to-lipid ratio (1:400), however, 1, 2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1, 2-diphytanoyl-sn-glycero-3-phosphoglycerol (DPhPG) liposomes did not exhibit any intensity anomaly with increasing temperature. This suggests that DPhPC and DPhPG liposomes are more loosely packed than PLFE liposomes; thus the branched methyl groups are not the contributing factor of the tight membrane packing found in PLFE liposomes. Using a multiexcitation method, we have also determined the average (R), in-plane (R(ip)), and out-of-plane (R(op)) rotational rates of perylene in PLFE liposomes at various temperatures (20-65 degrees C). R and R(ip), determined at two different probe-to-lipid ratios (1:400 and 1:3200), both undergo an abrupt increase when the temperature is elevated to approximately 48 degrees C. These data suggest that PLFE liposomes are rigid and tightly packed at low temperatures, but they begin to possess appreciable "membrane fluidity" at temperatures close to the minimum growth temperature ( approximately 50 degrees C) of thermoacidophilic archaebacteria.
Collapse
Affiliation(s)
- T K Khan
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
| | | |
Collapse
|
18
|
Baba T, Minamikawa H, Hato M, Motoki A, Hirano M, Zhou D, Kawasaki K. Synthetic phytanyl-chained glycolipid vesicle membrane as a novel matrix for functional reconstitution of cyanobacterial photosystem II complex. Biochem Biophys Res Commun 1999; 265:734-8. [PMID: 10600489 DOI: 10.1006/bbrc.1999.1754] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The vesicles composed of synthetic phytanyl-chained glycolipid and natural sulfoquinovosyldiacylglycerol at 9:1 molar ratio were successfully applied to functional reconstitution of photosystem II complex (PS II) from a thermophilic cyanobacterium. The synthetic glycolipid employed was one of our model archaeal diether lipids, 1, 3-di-O-phytanyl-2-O-(beta-D-maltotriosyl)glycerol. The light-induced oxygen-evolving activity of PS II reconstituted in the glycolipid vesicles was approximately 6-fold higher than that reconstituted in several phosphatidylcholine vesicles. The present results reveal the first evidence that a well-designed synthetic glycolipid is effective for the functional reconstitution of complicated and labile membrane protein complexes, such as PS II.
Collapse
Affiliation(s)
- T Baba
- Department of Polymer Physics, National Institute of Materials and Chemical Research (NIMC), 1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan
| | | | | | | | | | | | | |
Collapse
|
19
|
Elferink MG, van Breemen J, Konings WN, Driessen AJ, Wilschut J. Slow fusion of liposomes composed of membrane-spanning lipids. Chem Phys Lipids 1997; 88:37-43. [PMID: 9297853 DOI: 10.1016/s0009-3084(97)00044-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The fusion characteristics of large unilamellar liposomes composed of bipolar tetraether lipids extracted from the thermophilic archaeon Sulfolobus acidocaldarius, was investigated. These lipids span the entire membrane and form single monolayer liposomes in aqueous media [Elferink, M.G.L., de Wit, J.G., Demel, R., Driessen, A.J.M. and Konings, W.N., (1992) J. Biol. Chem. 267, 1375-1381]. In the presence of calcium-phosphate, slow mixing of the aqueous liposome contents and membrane lipids occurred, demonstrating that these liposomes are fusion-competent. The fusion process was essentially nonleaky. The rate of fusion increased with the pH and the concentration of calcium and phosphate. Fusion resulted in an increase of the size of the liposomes. These data demonstrate that a monolayer organization of lipids in a membrane does not per se interfere with membrane fusion competence.
Collapse
Affiliation(s)
- M G Elferink
- Department of Microbiology, University of Groningen, Haren, The Netherlands
| | | | | | | | | |
Collapse
|
20
|
Müller DJ, Amrein M, Engel A. Adsorption of biological molecules to a solid support for scanning probe microscopy. J Struct Biol 1997; 119:172-88. [PMID: 9245758 DOI: 10.1006/jsbi.1997.3875] [Citation(s) in RCA: 244] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Scanning probe microscopes are now established tools to study the surface structure of biological macromolecules under physiological conditions. Sample preparation methods for this microscopy all have the objective to attach the specimen firmly to a support. Here we analyse the commonly used method of adsorbing biological specimens to freshly cleaved mica. This is facilitated by adjusting the electrolyte concentration and the pH of the buffer solution. Native macromolecular systems absorbed to mica in this way can be reproducibly imaged at submolecular resolution.
Collapse
Affiliation(s)
- D J Müller
- M.E. Müller-Institute for Microscopy, University of Basel, Switzerland
| | | | | |
Collapse
|
21
|
De Rosa M. Archaeal lipids: structural features and supramolecular organization. THIN SOLID FILMS 1996; 284-285:13-17. [DOI: 10.1016/s0040-6090(96)08832-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
|
22
|
Giuffrè A, D'Itri E, Giannini S, Brunori M, Ubbink-Kok T, Konings WN, Antonini G. The caa3 terminal oxidase of Bacillus stearothermophilus. Transient spectroscopy of electron transfer and ligand binding. J Biol Chem 1996; 271:13987-92. [PMID: 8662862 DOI: 10.1074/jbc.271.24.13987] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The thermophilic bacterium Bacillus stearothermophilus possesses a caa3-type terminal oxidase, which was previously purified (De Vrij, W., Heyne, R. I. R., and Konings, W. N. (1989) Eur. J. Biochem. 178, 763-770). We have carried out extensive kinetic experiments on the purified enzyme by stopped-flow time-resolved optical spectroscopy combined with singular value decomposition analysis. The results indicate a striking similarity of behavior between this enzyme and the electrostatic complex between mammalian cytochrome c and cytochrome c oxidase. CO binding to fully reduced caa3 occurs with a second order rate constant (k = 7.8 x 10(4)M-1 s-1) and an activation energy (E* = 6.1 kcal mol-1) similar to those reported for beef heart cytochrome c oxidase. Dithionite reduces cytochrome a with bimolecular kinetics, while cytochrome a3 (and CuB) is reduced via intramolecular electron transfer. When the fully reduced enzyme is mixed with O2, cytochrome a3, and cytochrome c are rapidly oxidized, whereas cytochrome a remains largely reduced in the first few milliseconds. When cyanide-bound caa3 is mixed with ascorbate plus TMPD, cytochrome c and cytochrome a are synchronously reduced; the value of the second order rate constant (k = 3 x 10(5) M-1 s-1 at 30 degrees C) suggests that cytochrome c is the electron entry site. Steady-state experiments indicate that cytochrome a has a redox potential higher than cytochrome c. The data from the reaction with O2 reveal a remarkable similarity in the kinetic, equilibrium, and optical properties of caa3 and the electrostatic complex cytochrome c/cytochrome c oxidase.
Collapse
Affiliation(s)
- A Giuffrè
- Department of Biochemical Sciences and CNR Center of Molecular Biology, University of Rome "La Sapienza," 00185 Rome, Italy
| | | | | | | | | | | | | |
Collapse
|
23
|
Freisleben HJ, Zwicker K, Jezek P, John G, Bettin-Bogutzki A, Ring K, Nawroth T. Reconstitution of bacteriorhodopsin and ATP synthase from Micrococcus luteus into liposomes of the purified main tetraether lipid from Thermoplasma acidophilum: proton conductance and light-driven ATP synthesis. Chem Phys Lipids 1995; 78:137-47. [PMID: 8565113 DOI: 10.1016/0009-3084(95)02491-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The archaebacterium Thermoplasma acidophilum is cultivated at 59 degrees C in a medium containing sulfuric acid of pH 2. The purified bipolar membrane spanning main phospholipid (MPL) of this organism can be used to produce stable liposomes of 100-500 nm in diameter either using a French pressure cell detergent dialysis or sonication. Despite a potassium diffusion potential of 186 mV very low ionic permeability of sonicated MPL liposomes was measured using the potassium binding fluorescent indicator benzofuran isophthalate PBF1, which measures net K+ uptake. The latter also remained very low, in the presence of the K(+) ionophore valinomycin and palmitic acid. Addition of valinomycin and the potent uncoupler carbonylcyanid-p-trifluormehoxyphenyl-hydrazone (FCCP), led to a stimulation in potassium uptake. The rate of proton flux can be calculated from the net K(+) uptake. Under these conditions MPL liposomes are 1-2 orders of magnitude less permeable than egg yolk lecithin vesicles. The difference in proton permeability becomes even more pronounced with increasing temperature, examined using the fluorescent pH indicator pyranine. Purified bacteriorhodopsin from Halobacterium halobium was reconstituted into MPL liposomes in order to study the light-driven proton uptake in 150 mM KCl following addition of valinomycin, gramicidin, FCCP and Triton X-100. The light-driven proton transport into the liposomes was increased 30-fold by addition of valinomycin decreased by gramicidin and FCCP, and abolished by Triton X-100. Co-reconstituted MPL proteoliposomes containing bacteriorhodopsin and ATP synthase from Micrococcus luteus were capable of light-driven ATP synthesis demonstrating the functional coupling of proton transport and nucleotide generation in liposomal MPL membranes.
Collapse
Affiliation(s)
- H J Freisleben
- Klinikum der Johann Wolfgang Goether-Universität, Gustav-Embden-Zentrum der Biologischen Chemie, Laboratorium für Mikrobiologische Chemie, Frankfurt/M, Germany
| | | | | | | | | | | | | |
Collapse
|
24
|
Elferink MG, Bosma T, Lolkema JS, Gleiszner M, Driessen AJ, Konings WN. Thermostability of respiratory terminal oxidases in the lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1230:31-7. [PMID: 7612641 DOI: 10.1016/0005-2728(95)00028-h] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effect of the lipid environment on the thermostability of three respiratory terminal oxidases was determined. Cytochrome-c oxidase from beef heart and Bacillus stearothermophilus were used as representative proteins from mesophilic and thermophilic origin, respectively. Quinol oxidase from the archaeon Sulfolobus acidocaldarius represented the model for a extreme thermoacidophilic enzyme. All three integral membrane proteins were tested for their thermal inactivation in detergent and after reconstitution in liposomes composed of phospholipids of Escherichia coli or tetraether lipids from S. acidocaldarius. When preincubated at 0 degrees C, all three enzymes exhibited biphasic thermal inactivation curves. Data could be analysed according to a two-state model that defines two conformations of the enzyme, differing in their thermostability. Monophasic inactivation curves were observed when the enzymes were preincubated at higher temperatures prior to thermal inactivation. Lipids rendered the beef-heart cytochrome-c oxidase and S. acidocaldarius quinol oxidase more thermostable as compared to detergent solution. In contrast, the B. stearothermophilus oxidase, an intrinsically thermostable enzyme, was as thermostable in detergent as in the reconstituted state. These data suggest that the lipid environment can be an important factor in the thermostability of membrane proteins.
Collapse
Affiliation(s)
- M G Elferink
- Department of Microbiology, University of Groningen, Haren, The Netherlands
| | | | | | | | | | | |
Collapse
|
25
|
Affiliation(s)
- M Lübben
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, Germany
| |
Collapse
|
26
|
Gleissner M, Elferink MG, Driessen AJ, Konings WN, Anemüller S, Schäfer G. Generation of proton-motive force by an archaeal terminal quinol oxidase from Sulfolobus acidocaldarius. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 224:983-90. [PMID: 7925423 DOI: 10.1111/j.1432-1033.1994.00983.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The terminal quinol oxidase of the cytochrome aa3 type was isolated from the extreme thermoacidophilic archaeon Sulfolobus acidocaldarius. In micellar solution, the enzyme oxidized various quinols and exerted the highest activity with the physiological substrate caldariella quinol. The enzyme was functionally reconstituted into monolayer liposomes composed of archaeal tetraether lipids also derived from S. acidocaldarius. With the electron donor system ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine, the reconstituted enzyme was more active in the archaeal lipids as compared to lipids derived from Escherichia coli at temperatures above 50 degrees C. Due to the low proton permeability of the tetraether lipids, it was possible to generate a steady-state transmembrane electrical potential (delta psi, interior negative), and transmembrane pH gradient (delta pH, interior alkaline) at temperatures up to 70 degrees C. The successful functional reconstitution of the cytochrome aa3-type quinol oxidase from Sulfolobus identifies it as the key energy converter in the respiratory system of this hyperthermophilic archaeon.
Collapse
Affiliation(s)
- M Gleissner
- Institute of Biochemistry, Medical University of Lübeck, Germany
| | | | | | | | | | | |
Collapse
|
27
|
Elferink MG, de Wit JG, Driessen AJ, Konings WN. Stability and proton-permeability of liposomes composed of archaeal tetraether lipids. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1193:247-54. [PMID: 8054346 DOI: 10.1016/0005-2736(94)90160-0] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Liposomes composed of tetraether lipids originating from the thermoacidophilic archaeon Sulfolobus acidocaldarius were analyzed for their stability and proton permeability from 20 degrees C up to 80 degrees C. At room temperature, these liposomes are considerably more stable and have a much lower proton permeability than liposomes composed of diester lipids originating from the mesophilic bacterium Escherichia coli or the thermophilic bacterium Bacillus stearothermophilus. With increasing temperature, the stability decreased and the proton permeability increased for all liposomes. Liposomes composed from tetraether lipids, however, remain the most stable. These data suggest these liposomes retain the rigidity of the cytoplasmic membrane of S. acidocaldarius needed to endure extreme environmental growth conditions.
Collapse
Affiliation(s)
- M G Elferink
- Department of Microbiology, University of Groningen, Haren, The Netherlands
| | | | | | | |
Collapse
|
28
|
Veld GI, Driessen AJ, Konings WN. Bacterial solute transport proteins in their lipid environment. FEMS Microbiol Rev 1993; 12:293-314. [PMID: 8268004 DOI: 10.1111/j.1574-6976.1993.tb00024.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The cytoplasmic membrane of bacteria is a selective barrier that restricts entry and exit of solutes. Transport of solutes across this membrane is catalyzed by specific membrane proteins. Integral membrane proteins usually require specific lipids for optimal activity and are inhibited by other lipid species. Their activities are also sensitive to the lipid bilayer dynamics and physico-chemical state. Bacteria can adapt to changes in the environments (respective temperature, hydrostatic pressure, and pH) by altering the lipid composition of the membrane. Homeoviscous adaptation results in the maintenance of the liquid-crystalline phase through alterations in the degree of acyl chain saturation and branching, acyl chain length and the sterol content of the membrane. Homeophasic adaptation prevents the formation of non-bilayer phases, which would disrupt membrane organization and increase permeability. A balance is maintained between the lamellar phase, preferring lipids, and those that adopt a non-bilayer organization. As a result, the membrane proteins are optimally active under physiological conditions. The molecular basis of lipid-protein interactions is still obscure. Annular lipids stabilize integral membrane proteins. Stabilization occurs through electrostatic and possibly other interactions between the lipid headgroups and the charged amino acid residues close to the phospholipid-water interface, and hydrophobic interactions between the fatty acyl chains and the membrane-spanning segments. Reconstitution techniques allow manipulation of the lipid composition of the membrane in a way that is difficult to achieve in vivo. The physical characteristics of membrane lipids that affect protein-mediated transport functions have been studied in liposomal systems that separate an inner and outer compartment. The activity of most transport proteins is modulated by the bulk physical characteristics of the lipid bilayer, while specific lipid requirements appear rare.
Collapse
Affiliation(s)
- G I Veld
- Department of Microbiology, University of Groningen, The Netherlands
| | | | | |
Collapse
|