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Ihara K, Kim S, Ando T, Yoneyama H. Importance of transmembrane helix 4 of l-alanine exporter AlaE in oligomer formation and substrate export activity in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35275050 DOI: 10.1099/mic.0.001147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
AlaE is the smallest amino acid exporter identified in Escherichia coli. It exports l-alanine using the proton motive force and plays a pivotal role in maintaining intracellular l-alanine homeostasis by acting as a safety valve. However, our understanding of the molecular mechanisms of substrate export by AlaE is still limited because structural information is lacking. Due to its small size (149 amino acid residues), it has been speculated that AlaE functions by forming an oligomer. In this study, we performed chemical cross-linking and pull-down assays and showed that AlaE indeed generates homo-oligomers as a functional unit. Previous random mutagenesis experiments identified three loss-of-function AlaE point mutations in the predicted transmembrane helix 4 (TM4) region, two of which are present in the GxxxG motif. When alanine-scanning mutagenesis was applied to the TM4 region, the AlaE derivatives that had amino acid substitutions around the GxxxG motif showed low l-alanine export activities, indicating that the GxxxG motif in TM4 plays an important role in substrate export. However, these AlaE variants with low activity could still form oligomers. We therefore concluded that AlaE forms homo-oligomers and that the GxxxG motif in the TM4 region plays an essential role in AlaE activity but is not involved in AlaE oligomer formation.
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Affiliation(s)
- Kohei Ihara
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
| | - Seryoung Kim
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
| | - Tasuke Ando
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
| | - Hiroshi Yoneyama
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
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Medrano-Soto A, Ghazi F, Hendargo KJ, Moreno-Hagelsieb G, Myers S, Saier MH. Expansion of the Transporter-Opsin-G protein-coupled receptor superfamily with five new protein families. PLoS One 2020; 15:e0231085. [PMID: 32320418 PMCID: PMC7176098 DOI: 10.1371/journal.pone.0231085] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 03/17/2020] [Indexed: 02/06/2023] Open
Abstract
Here we provide bioinformatic evidence that the Organo-Arsenical Exporter (ArsP), Endoplasmic Reticulum Retention Receptor (KDELR), Mitochondrial Pyruvate Carrier (MPC), L-Alanine Exporter (AlaE), and the Lipid-linked Sugar Translocase (LST) protein families are members of the Transporter-Opsin-G Protein-coupled Receptor (TOG) Superfamily. These families share domains homologous to well-established TOG superfamily members, and their topologies of transmembranal segments (TMSs) are compatible with the basic 4-TMS repeat unit characteristic of this Superfamily. These repeat units tend to occur twice in proteins as a result of intragenic duplication events, often with subsequent gain/loss of TMSs in many superfamily members. Transporters within the ArsP family allow microbial pathogens to expel toxic arsenic compounds from the cell. Members of the KDELR family are involved in the selective retrieval of proteins that reside in the endoplasmic reticulum. Proteins of the MPC family are involved in the transport of pyruvate into mitochondria, providing the organelle with a major oxidative fuel. Members of family AlaE excrete L-alanine from the cell. Members of the LST family are involved in the translocation of lipid-linked glucose across the membrane. These five families substantially expand the range of substrates of transport carriers in the superfamily, although KDEL receptors have no known transport function. Clustering of protein sequences reveals the relationships among families, and the resulting tree correlates well with the degrees of sequence similarity documented between families. The analyses and programs developed to detect distant relatedness, provide insights into the structural, functional, and evolutionary relationships that exist between families of the TOG superfamily, and should be of value to many other investigators.
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Affiliation(s)
- Arturo Medrano-Soto
- Department of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Faezeh Ghazi
- Department of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Kevin J. Hendargo
- Department of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | | | - Scott Myers
- Department of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Milton H. Saier
- Department of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California, United States of America
- * E-mail:
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Ran P, Zhu S, Song J, Wu J, Mo F, Fu Y. A widened emission window of the peroxydisulfate-oxygen system for the detection of L-alanine. Colloids Surf B Biointerfaces 2018; 169:418-421. [PMID: 29807340 DOI: 10.1016/j.colsurfb.2018.05.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 04/12/2018] [Accepted: 05/16/2018] [Indexed: 12/20/2022]
Abstract
Peroxydisulfate-oxygen (S2O82--O2) system has become one of the most used systems in electrogenerated chemiluminscence (ECL) field. Due to S2O82- can be used as Fenton Reagent, this work designed an ECL biosensor based on the S2O82--O2 system for the detection of L-alanine in a widened emission window and using hemin/G-quadruplex and platinum and palladium nanowires (Pt-Pd NWs) to in situ generate O2 to amplify the ECL intensity. The proposed ECL sensor showed an excellent analytical property for the detection of L-alanine in a linear range of 5.0 × 10-3 M to 1.0 × 10-8 M with the detection limit of 3.3 × 10-9 M (S/N = 3). This work with high selectivity, stability and reproducibility may open a new door to apply S2O82- in ECL field.
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Affiliation(s)
- Peiyao Ran
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
| | - Shu Zhu
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
| | - Jinyi Song
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
| | - Jingling Wu
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
| | - Fangjing Mo
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
| | - Yingzi Fu
- Key Laboratory on Luminescence and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China.
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Ihara K, Sato K, Hori H, Makino Y, Shigenobu S, Ando T, Isogai E, Yoneyama H. Expression of the alaE gene is positively regulated by the global regulator Lrp in response to intracellular accumulation of l-alanine in Escherichia coli. J Biosci Bioeng 2017; 123:444-450. [PMID: 28057466 DOI: 10.1016/j.jbiosc.2016.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/10/2016] [Accepted: 11/29/2016] [Indexed: 10/20/2022]
Abstract
The alaE gene in Escherichia coli encodes an l-alanine exporter that catalyzes the active export of l-alanine using proton electrochemical potential. In our previous study, alaE expression was shown to increase in the presence of l-alanyl-l-alanine (Ala-Ala). In this study, the global regulator leucine-responsive regulatory protein (Lrp) was identified as an activator of the alaE gene. A promoter less β-galactosidase gene was fused to an alaE upstream region (240 nucleotides). Cells that were lacZ-deficient and harbored this reporter plasmid showed significant induction of β-galactosidase activity (approximately 17-fold) in the presence of 6 mM l-alanine, l-leucine, and Ala-Ala. However, a reporter plasmid possessing a smaller alaE upstream region (180 nucleotides) yielded transformants with strikingly low enzyme activity under the same conditions. In contrast, lrp-deficient cells showed almost no β-galactosidase induction, indicating that Lrp positively regulates alaE expression. We next performed an electrophoretic mobility shift assay (EMSA) and a DNase I footprinting assay using purified hexahistidine-tagged Lrp (Lrp-His). Consequently, we found that Lrp-His binds to the alaE upstream region spanning nucleotide -161 to -83 with a physiologically relevant affinity (apparent KD, 288.7 ± 83.8 nM). Furthermore, the binding affinity of Lrp-His toward its cis-element was increased by l-alanine and l-leucine, but not by Ala-Ala and d-alanine. Based on these results, we concluded that the gene expression of the alaE is regulated by Lrp in response to intracellular levels of l-alanine, which eventually leads to intracellular homeostasis of l-alanine concentrations.
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Affiliation(s)
- Kohei Ihara
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Kazuki Sato
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Hatsuhiro Hori
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Yumiko Makino
- NIBB Core Research Facilities, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki 444-8585, Aichi, Japan
| | - Shuji Shigenobu
- NIBB Core Research Facilities, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki 444-8585, Aichi, Japan
| | - Tasuke Ando
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Emiko Isogai
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Hiroshi Yoneyama
- Laboratory of Animal Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan.
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