2NPK

An unusual twin-His arrangement in the pore of ammonia channels is essential for substrate conductance

Summary for 2NPK

• Entry DOI: 10.2210/pdb2npk/pdb
• Related: 1U7G 1XQE 1XQF 2NMR 2NOP 2NOW 2NPC 2NPD 2NPE 2NPG 2NPJ
• Descriptor: Ammonia channel, SULFATE ION, ACETATE ION, ... (6 entities in total)
• Functional Keywords: membrane protein, ammonia transport, histidine double mutant, amtb, transport protein
• Biological source: Escherichia coli
• Cellular location: Cell inner membrane; Multi-pass membrane protein: P69681
• Total number of polymer chains: 1
• Total formula weight: 44729.93

Authors

Lupo, D.,Winkler, F.K. (deposition date: 2006-10-27, release date: 2006-11-14, Last modification date: 2023-10-25)

Primary citation

Javelle, A.,Lupo, D.,Zheng, L.,Li, X.-D.,Winkler, F.K.,Merrick, M.
An unusual twin-his arrangement in the pore of ammonia channels is essential for substrate conductance
J.Biol.Chem., 281:39492-39498, 2006

PubMed Abstract: 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.

PubMed: 17040913
DOI: 10.1074/jbc.M608325200

Experimental method

X-RAY DIFFRACTION (2 Å)