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Spermidine Binding to the Acetinobacter baumannii Efflux Protein AceI Observed by Near-UV Synchrotron Radiation Circular Dichroism Spectroscopy. RADIATION 2022. [DOI: 10.3390/radiation2020016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The aim of this work was to test polyamines as potential natural substrates of the Acinetobacter baumannii chlorhexidine efflux protein AceI using near-UV synchrotron radiation circular dichroism (SRCD) spectroscopy. The Gram-negative bacterium A. Baumannii is a leading cause of hospital-acquired infections and an important foodborne pathogen. A. Baumannii strains are becoming increasingly resistant to antimicrobial agents, including the synthetic antiseptic chlorhexidine. AceI (144-residues) was the founding member of the recently recognised PACE family of bacterial multidrug efflux proteins. Using the plasmid construct pTTQ18-aceI(His6) containing the A. baumannii aceI gene directly upstream from a His6-tag coding sequence, expression of AceI(His6) was amplified in E. coli BL21(DE3) cells. Near-UV (250–340 nm) SRCD measurements were performed on detergent-solubilised and purified AceI(His6) at 20 °C. Sample and SRCD experimental conditions were identified that detected binding of the triamine spermidine to AceI(His6). In a titration with spermidine (0–10 mM), this binding was saturable and fitting of the curve for the change in signal intensity produced an apparent binding affinity (KD) of 3.97 ± 0.45 mM. These SRCD results were the first experimental evidence obtained for polyamines as natural substrates of PACE proteins.
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Saidijam M, Karimi Dermani F, Sohrabi S, Patching SG. Efflux proteins at the blood-brain barrier: review and bioinformatics analysis. Xenobiotica 2017; 48:506-532. [PMID: 28481715 DOI: 10.1080/00498254.2017.1328148] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1. Efflux proteins at the blood-brain barrier provide a mechanism for export of waste products of normal metabolism from the brain and help to maintain brain homeostasis. They also prevent entry into the brain of a wide range of potentially harmful compounds such as drugs and xenobiotics. 2. Conversely, efflux proteins also hinder delivery of therapeutic drugs to the brain and central nervous system used to treat brain tumours and neurological disorders. For bypassing efflux proteins, a comprehensive understanding of their structures, functions and molecular mechanisms is necessary, along with new strategies and technologies for delivery of drugs across the blood-brain barrier. 3. We review efflux proteins at the blood-brain barrier, classified as either ATP-binding cassette (ABC) transporters (P-gp, BCRP, MRPs) or solute carrier (SLC) transporters (OATP1A2, OATP1A4, OATP1C1, OATP2B1, OAT3, EAATs, PMAT/hENT4 and MATE1). 4. This includes information about substrate and inhibitor specificity, structural organisation and mechanism, membrane localisation, regulation of expression and activity, effects of diseases and conditions and the principal technique used for in vivo analysis of efflux protein activity: positron emission tomography (PET). 5. We also performed analyses of evolutionary relationships, membrane topologies and amino acid compositions of the proteins, and linked these to structure and function.
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Affiliation(s)
- Massoud Saidijam
- a Department of Molecular Medicine and Genetics , Research Centre for Molecular Medicine, School of Medicine, Hamadan University of Medical Sciences , Hamadan , Iran and
| | - Fatemeh Karimi Dermani
- a Department of Molecular Medicine and Genetics , Research Centre for Molecular Medicine, School of Medicine, Hamadan University of Medical Sciences , Hamadan , Iran and
| | - Sareh Sohrabi
- a Department of Molecular Medicine and Genetics , Research Centre for Molecular Medicine, School of Medicine, Hamadan University of Medical Sciences , Hamadan , Iran and
| | - Simon G Patching
- b School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds , Leeds , UK
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Gupta AM, Mandal S. Mycobacterium tuberculosis H37 Rv1222: structural insight in transcription inhibition. J Biomol Struct Dyn 2017; 35:1574-1581. [DOI: 10.1080/07391102.2016.1189357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Aayatti Mallick Gupta
- Department of Microbiology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700019, India
| | - Sukhendu Mandal
- Department of Microbiology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700019, India
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Saidijam M, Azizpour S, Patching SG. Comprehensive analysis of the numbers, lengths and amino acid compositions of transmembrane helices in prokaryotic, eukaryotic and viral integral membrane proteins of high-resolution structure. J Biomol Struct Dyn 2017; 36:443-464. [PMID: 28150531 DOI: 10.1080/07391102.2017.1285725] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report a comprehensive analysis of the numbers, lengths and amino acid compositions of transmembrane helices in 235 high-resolution structures of integral membrane proteins. The properties of 1551 transmembrane helices in the structures were compared with those obtained by analysis of the same amino acid sequences using topology prediction tools. Explanations for the 81 (5.2%) missing or additional transmembrane helices in the prediction results were identified. Main reasons for missing transmembrane helices were mis-identification of N-terminal signal peptides, breaks in α-helix conformation or charged residues in the middle of transmembrane helices and transmembrane helices with unusual amino acid composition. The main reason for additional transmembrane helices was mis-identification of amphipathic helices, extramembrane helices or hairpin re-entrant loops. Transmembrane helix length had an overall median of 24 residues and an average of 24.9 ± 7.0 residues and the most common length was 23 residues. The overall content of residues in transmembrane helices as a percentage of the full proteins had a median of 56.8% and an average of 55.7 ± 16.0%. Amino acid composition was analysed for the full proteins, transmembrane helices and extramembrane regions. Individual proteins or types of proteins with transmembrane helices containing extremes in contents of individual amino acids or combinations of amino acids with similar physicochemical properties were identified and linked to structure and/or function. In addition to overall median and average values, all results were analysed for proteins originating from different types of organism (prokaryotic, eukaryotic, viral) and for subgroups of receptors, channels, transporters and others.
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Affiliation(s)
- Massoud Saidijam
- a Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine , Hamadan University of Medical Sciences , Hamadan , Iran
| | - Sonia Azizpour
- a Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine , Hamadan University of Medical Sciences , Hamadan , Iran
| | - Simon G Patching
- b School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology , University of Leeds , Leeds , UK
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Characterisation of the DAACS Family Escherichia coli Glutamate/Aspartate-Proton Symporter GltP Using Computational, Chemical, Biochemical and Biophysical Methods. J Membr Biol 2016; 250:145-162. [DOI: 10.1007/s00232-016-9942-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 12/09/2016] [Indexed: 10/20/2022]
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Saidijam M, Azizpour S, Patching SG. Amino acid composition analysis of human secondary transport proteins and implications for reliable membrane topology prediction. J Biomol Struct Dyn 2016; 35:929-949. [PMID: 27159787 DOI: 10.1080/07391102.2016.1167622] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Secondary transporters in humans are a large group of proteins that transport a wide range of ions, metals, organic and inorganic solutes involved in energy transduction, control of membrane potential and osmotic balance, metabolic processes and in the absorption or efflux of drugs and xenobiotics. They are also emerging as important targets for development of new drugs and as target sites for drug delivery to specific organs or tissues. We have performed amino acid composition (AAC) and phylogenetic analyses and membrane topology predictions for 336 human secondary transport proteins and used the results to confirm protein classification and to look for trends and correlations with structural domains and specific substrates and/or function. Some proteins showed statistically high contents of individual amino acids or of groups of amino acids with similar physicochemical properties. One recurring trend was a correlation between high contents of charged and/or polar residues with misleading results in predictions of membrane topology, which was especially prevalent in Mitochondrial Carrier family proteins. We demonstrate how charged or polar residues located in the middle of transmembrane helices can interfere with their identification by membrane topology tools resulting in missed helices in the prediction. Comparison of AAC in the human proteins with that in 235 secondary transport proteins from Escherichia coli revealed similar overall trends along with differences in average contents for some individual amino acids and groups of similar amino acids that are presumed to result from a greater number of functions and complexity in the higher organism.
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Affiliation(s)
- Massoud Saidijam
- a Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine , Hamadan University of Medical Sciences , Hamadan , Iran
| | - Sonia Azizpour
- a Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine , Hamadan University of Medical Sciences , Hamadan , Iran
| | - Simon G Patching
- b School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology , University of Leeds , Leeds LS2 9JT , UK
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Ma P, Patching SG, Ivanova E, Baldwin JM, Sharples D, Baldwin SA, Henderson PJF. Allantoin transport protein, PucI, from Bacillus subtilis: evolutionary relationships, amplified expression, activity and specificity. MICROBIOLOGY-SGM 2016; 162:823-836. [PMID: 26967546 DOI: 10.1099/mic.0.000266] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
This work reports the evolutionary relationships, amplified expression, functional characterization and purification of the putative allantoin transport protein, PucI, from Bacillus subtilis. Sequence alignments and phylogenetic analysis confirmed close evolutionary relationships between PucI and membrane proteins of the nucleobase-cation-symport-1 family of secondary active transporters. These include the sodium-coupled hydantoin transport protein, Mhp1, from Microbacterium liquefaciens, and related proteins from bacteria, fungi and plants. Membrane topology predictions for PucI were consistent with 12 putative transmembrane-spanning α-helices with both N- and C-terminal ends at the cytoplasmic side of the membrane. The pucI gene was cloned into the IPTG-inducible plasmid pTTQ18 upstream from an in-frame hexahistidine tag and conditions determined for optimal amplified expression of the PucI(His6) protein in Escherichia coli to a level of about 5 % in inner membranes. Initial rates of inducible PucI-mediated uptake of 14C-allantoin into energized E. coli whole cells conformed to Michaelis-Menten kinetics with an apparent affinity (Kmapp) of 24 ± 3 μM, therefore confirming that PucI is a medium-affinity transporter of allantoin. Dependence of allantoin transport on sodium was not apparent. Competitive uptake experiments showed that PucI recognizes some additional hydantoin compounds, including hydantoin itself, and to a lesser extent a range of nucleobases and nucleosides. PucI(His6) was solubilized from inner membranes using n-dodecyl-β-d-maltoside and purified. The isolated protein contained a substantial proportion of α-helix secondary structure, consistent with the predictions, and a 3D model was therefore constructed on a template of the Mhp1 structure, which aided localization of the potential ligand binding site in PucI.
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Affiliation(s)
- Pikyee Ma
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Simon G Patching
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Ekaterina Ivanova
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Jocelyn M Baldwin
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - David Sharples
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Stephen A Baldwin
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Peter J F Henderson
- School of BioMedical Sciences and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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