Mapping the kidney potassium channel ROMK1

Glycosylation of the pore sequence and the COOH terminus

Ruth A. Schwalbe, Laura Bianchi, Arthur M. Brown

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

ROMK1, also known as Kir 1.1, is an inwardly rectifying K+ channel and is the prototypical member of the large Kir gene family. The accepted model of Kir topology predicts intracellular NH2 and COOH termini, and two membrane-spanning segments, M1 and M2, connected by an intramembranous pore- forming segment, H5. The sequence of H5 is similar in voltage-dependent K+ channels and features a strictly conserved GY/FG in its mid-region, which has been proposed as the selectivity filter of the pore. We have been using N- glycosylation substitution mutants to map the extracellular topology of ROMK1 biochemically and have described several loci in H5 that were glycosylated. We now report glycosylation at loci Tyr144 and Phe146, which indicates that the signature GYG sequence (143-145) rather than being intramembranous is extracellular. The COOH terminus was predicted to begin at position 178, but contrary to the model, we observed that position 257 was glycosylated and surrounding positions at 199, 222, and 298 were unglycosylated. N- Glycosylation sequon substitution at the latter three positions abolished K+/Na+ selectivity. Our results suggest a major revision of the topology of ROMK1 with H5 and the pore signature sequence now completely extracellular. The COOH terminus appears to form two additional membrane-spanning segments and to contribute to the ion conduction pathway.

Original languageEnglish
Pages (from-to)25217-25223
Number of pages7
JournalJournal of Biological Chemistry
Volume272
Issue number40
DOIs
StatePublished - Oct 3 1997
Externally publishedYes

Fingerprint

Glycosylation
Potassium Channels
Topology
Kidney
Substitution reactions
Inwardly Rectifying Potassium Channel
Membranes
Genes
Ions
Electric potential

ASJC Scopus subject areas

  • Biochemistry

Cite this

Mapping the kidney potassium channel ROMK1 : Glycosylation of the pore sequence and the COOH terminus. / Schwalbe, Ruth A.; Bianchi, Laura; Brown, Arthur M.

In: Journal of Biological Chemistry, Vol. 272, No. 40, 03.10.1997, p. 25217-25223.

Research output: Contribution to journalArticle

@article{65f3294a52494a42bd6155302b2b9bdf,
title = "Mapping the kidney potassium channel ROMK1: Glycosylation of the pore sequence and the COOH terminus",
abstract = "ROMK1, also known as Kir 1.1, is an inwardly rectifying K+ channel and is the prototypical member of the large Kir gene family. The accepted model of Kir topology predicts intracellular NH2 and COOH termini, and two membrane-spanning segments, M1 and M2, connected by an intramembranous pore- forming segment, H5. The sequence of H5 is similar in voltage-dependent K+ channels and features a strictly conserved GY/FG in its mid-region, which has been proposed as the selectivity filter of the pore. We have been using N- glycosylation substitution mutants to map the extracellular topology of ROMK1 biochemically and have described several loci in H5 that were glycosylated. We now report glycosylation at loci Tyr144 and Phe146, which indicates that the signature GYG sequence (143-145) rather than being intramembranous is extracellular. The COOH terminus was predicted to begin at position 178, but contrary to the model, we observed that position 257 was glycosylated and surrounding positions at 199, 222, and 298 were unglycosylated. N- Glycosylation sequon substitution at the latter three positions abolished K+/Na+ selectivity. Our results suggest a major revision of the topology of ROMK1 with H5 and the pore signature sequence now completely extracellular. The COOH terminus appears to form two additional membrane-spanning segments and to contribute to the ion conduction pathway.",
author = "Schwalbe, {Ruth A.} and Laura Bianchi and Brown, {Arthur M.}",
year = "1997",
month = "10",
day = "3",
doi = "10.1074/jbc.272.40.25217",
language = "English",
volume = "272",
pages = "25217--25223",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "40",

}

TY - JOUR

T1 - Mapping the kidney potassium channel ROMK1

T2 - Glycosylation of the pore sequence and the COOH terminus

AU - Schwalbe, Ruth A.

AU - Bianchi, Laura

AU - Brown, Arthur M.

PY - 1997/10/3

Y1 - 1997/10/3

N2 - ROMK1, also known as Kir 1.1, is an inwardly rectifying K+ channel and is the prototypical member of the large Kir gene family. The accepted model of Kir topology predicts intracellular NH2 and COOH termini, and two membrane-spanning segments, M1 and M2, connected by an intramembranous pore- forming segment, H5. The sequence of H5 is similar in voltage-dependent K+ channels and features a strictly conserved GY/FG in its mid-region, which has been proposed as the selectivity filter of the pore. We have been using N- glycosylation substitution mutants to map the extracellular topology of ROMK1 biochemically and have described several loci in H5 that were glycosylated. We now report glycosylation at loci Tyr144 and Phe146, which indicates that the signature GYG sequence (143-145) rather than being intramembranous is extracellular. The COOH terminus was predicted to begin at position 178, but contrary to the model, we observed that position 257 was glycosylated and surrounding positions at 199, 222, and 298 were unglycosylated. N- Glycosylation sequon substitution at the latter three positions abolished K+/Na+ selectivity. Our results suggest a major revision of the topology of ROMK1 with H5 and the pore signature sequence now completely extracellular. The COOH terminus appears to form two additional membrane-spanning segments and to contribute to the ion conduction pathway.

AB - ROMK1, also known as Kir 1.1, is an inwardly rectifying K+ channel and is the prototypical member of the large Kir gene family. The accepted model of Kir topology predicts intracellular NH2 and COOH termini, and two membrane-spanning segments, M1 and M2, connected by an intramembranous pore- forming segment, H5. The sequence of H5 is similar in voltage-dependent K+ channels and features a strictly conserved GY/FG in its mid-region, which has been proposed as the selectivity filter of the pore. We have been using N- glycosylation substitution mutants to map the extracellular topology of ROMK1 biochemically and have described several loci in H5 that were glycosylated. We now report glycosylation at loci Tyr144 and Phe146, which indicates that the signature GYG sequence (143-145) rather than being intramembranous is extracellular. The COOH terminus was predicted to begin at position 178, but contrary to the model, we observed that position 257 was glycosylated and surrounding positions at 199, 222, and 298 were unglycosylated. N- Glycosylation sequon substitution at the latter three positions abolished K+/Na+ selectivity. Our results suggest a major revision of the topology of ROMK1 with H5 and the pore signature sequence now completely extracellular. The COOH terminus appears to form two additional membrane-spanning segments and to contribute to the ion conduction pathway.

UR - http://www.scopus.com/inward/record.url?scp=0030823286&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030823286&partnerID=8YFLogxK

U2 - 10.1074/jbc.272.40.25217

DO - 10.1074/jbc.272.40.25217

M3 - Article

VL - 272

SP - 25217

EP - 25223

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 40

ER -