An Unusual Twin-His Arrangement in the Pore of Ammonia Channels Is Essential for Substrate Conductance

Amt proteins constitute a class of ubiquitous integral membrane proteins that mediate movement of ammonium across cell membranes. They are homotrimers, in which each subunit contains a narrow pore through which substrate transport occurs. Two conserved histidine residues in the pore have been propos...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 2006-12, Vol.281 (51), p.39492-39498
Main Authors: Javelle, Arnaud, Lupo, Domenico, Zheng, Lei, Li, Xiao-Dan, Winkler, Fritz K., Merrick, Mike
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Ammonia - chemistry
Cation Transport Proteins - chemistry
Electrons
Escherichia coli
Escherichia coli - enzymology
Escherichia coli - metabolism
Escherichia coli Proteins - chemistry
Genotype
Histidine - chemistry
Models, Chemical
Molecular Sequence Data
Mutation
Nucleotidyltransferases - chemistry
PII Nitrogen Regulatory Proteins - chemistry
Plasmids - metabolism
Protein Binding
Protein Conformation
Substrate Specificity
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Amt proteins constitute a class of ubiquitous integral membrane proteins that mediate movement of ammonium across cell membranes. They are homotrimers, in which each subunit contains a narrow pore through which substrate transport occurs. Two conserved histidine residues in the pore have been proposed to be necessary for ammonia conductance. By analyzing 14 engineered polar and non-polar variants of these histidines, in Escherichia coli AmtB, we show that both histidines are absolutely required for optimum substrate conductance. Crystal structures of variants confirm that substitution of the histidine residues does not affect AmtB structure. In a subgroup of Amt proteins, found only in fungi, one of the histidines is replaced by glutamate. The equivalent substitution in E. coli AmtB is partially active, and the structure of this variant suggests that the glutamate side chain can make similar interactions to those made by histidine.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M608325200