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Wide tolerance to amino acids substitutions in the OCTN1 ergothioneine transporter.
Biochim Biophys Acta. 2016 Jun; 1860(6):1334-42.BB

Abstract

BACKGROUND

Organic cation transporters transfer solutes with a positive charge across the plasma membrane. The novel organic cation transporter 1 (OCTN1) and 2 (OCTN2) transport ergothioneine and carnitine, respectively. Mutations in the SLC22A5 gene encoding OCTN2 cause primary carnitine deficiency, a recessive disorders resulting in low carnitine levels and defective fatty acid oxidation. Variations in the SLC22A4 gene encoding OCTN1 are associated with rheumatoid arthritis and Crohn disease.

METHODS

Here we evaluate the functional properties of the OCTN1 transporter using chimeric transporters constructed by fusing different portion of the OCTN1 and OCTN2 cDNAs. Their relative abundance and subcellular distribution was evaluated through western blot analysis and confocal microscopy.

RESULTS

Substitutions of the C-terminal portion of OCTN1 with the correspondent residues of OCTN2 generated chimeric OCTN transporters more active than wild-type OCTN1 in transporting ergothioneine. Additional single amino acid substitutions introduced in chimeric OCTN transporters further increased ergothioneine transport activity. Kinetic analysis indicated that increased transport activity was due to an increased V(max), with modest changes in K(m) toward ergothioneine.

CONCLUSIONS

Our results indicate that the OCTN1 transporter is tolerant to extensive amino acid substitutions. This is in sharp contrast to the OCTN2 carnitine transporter that has been selected for high functional activity through evolution, with almost all substitutions reducing carnitine transport activity.

GENERAL SIGNIFICANCE

The widespread tolerance of OCTN1 to amino acid substitutions suggests that the corresponding SLC22A4 gene may have derived from a recent duplication of the SLC22A5 gene and might not yet have a defined physiological role.

Authors+Show Affiliations

Division of Medical Genetics, Departments of Pediatrics and Pathology, University of Utah, Salt Lake City, UT 84108, United States.Division of Medical Genetics, Departments of Pediatrics and Pathology, University of Utah, Salt Lake City, UT 84108, United States; Department of Basic Medical Sciences, University of Bari, Policlinico, I-70124 Bari, Italy.Division of Medical Genetics, Departments of Pediatrics and Pathology, University of Utah, Salt Lake City, UT 84108, United States.Division of Medical Genetics, Departments of Pediatrics and Pathology, University of Utah, Salt Lake City, UT 84108, United States. Electronic address: Nicola.Longo@hsc.utah.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

26994919

Citation

Frigeni, Marta, et al. "Wide Tolerance to Amino Acids Substitutions in the OCTN1 Ergothioneine Transporter." Biochimica Et Biophysica Acta, vol. 1860, no. 6, 2016, pp. 1334-42.
Frigeni M, Iacobazzi F, Yin X, et al. Wide tolerance to amino acids substitutions in the OCTN1 ergothioneine transporter. Biochim Biophys Acta. 2016;1860(6):1334-42.
Frigeni, M., Iacobazzi, F., Yin, X., & Longo, N. (2016). Wide tolerance to amino acids substitutions in the OCTN1 ergothioneine transporter. Biochimica Et Biophysica Acta, 1860(6), 1334-42. https://doi.org/10.1016/j.bbagen.2016.03.021
Frigeni M, et al. Wide Tolerance to Amino Acids Substitutions in the OCTN1 Ergothioneine Transporter. Biochim Biophys Acta. 2016;1860(6):1334-42. PubMed PMID: 26994919.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Wide tolerance to amino acids substitutions in the OCTN1 ergothioneine transporter. AU - Frigeni,Marta, AU - Iacobazzi,Francesco, AU - Yin,Xue, AU - Longo,Nicola, Y1 - 2016/03/16/ PY - 2015/07/09/received PY - 2016/02/24/revised PY - 2016/03/15/accepted PY - 2016/3/21/entrez PY - 2016/3/21/pubmed PY - 2016/8/2/medline KW - Ergothioneine transport KW - OCTN1 KW - OCTN2 KW - Organic cation transporters KW - SLC22A4 KW - SLC22A5 SP - 1334 EP - 42 JF - Biochimica et biophysica acta JO - Biochim Biophys Acta VL - 1860 IS - 6 N2 - BACKGROUND: Organic cation transporters transfer solutes with a positive charge across the plasma membrane. The novel organic cation transporter 1 (OCTN1) and 2 (OCTN2) transport ergothioneine and carnitine, respectively. Mutations in the SLC22A5 gene encoding OCTN2 cause primary carnitine deficiency, a recessive disorders resulting in low carnitine levels and defective fatty acid oxidation. Variations in the SLC22A4 gene encoding OCTN1 are associated with rheumatoid arthritis and Crohn disease. METHODS: Here we evaluate the functional properties of the OCTN1 transporter using chimeric transporters constructed by fusing different portion of the OCTN1 and OCTN2 cDNAs. Their relative abundance and subcellular distribution was evaluated through western blot analysis and confocal microscopy. RESULTS: Substitutions of the C-terminal portion of OCTN1 with the correspondent residues of OCTN2 generated chimeric OCTN transporters more active than wild-type OCTN1 in transporting ergothioneine. Additional single amino acid substitutions introduced in chimeric OCTN transporters further increased ergothioneine transport activity. Kinetic analysis indicated that increased transport activity was due to an increased V(max), with modest changes in K(m) toward ergothioneine. CONCLUSIONS: Our results indicate that the OCTN1 transporter is tolerant to extensive amino acid substitutions. This is in sharp contrast to the OCTN2 carnitine transporter that has been selected for high functional activity through evolution, with almost all substitutions reducing carnitine transport activity. GENERAL SIGNIFICANCE: The widespread tolerance of OCTN1 to amino acid substitutions suggests that the corresponding SLC22A4 gene may have derived from a recent duplication of the SLC22A5 gene and might not yet have a defined physiological role. SN - 0006-3002 UR - https://www.unboundmedicine.com/medline/citation/26994919/Wide_tolerance_to_amino_acids_substitutions_in_the_OCTN1_ergothioneine_transporter_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0304-4165(16)30076-9 DB - PRIME DP - Unbound Medicine ER -