3b9y
From Proteopedia
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Crystal structure of the Nitrosomonas europaea Rh protein
Overview
Amt/MEP/Rh proteins are a family of integral membrane proteins implicated, in the transport of NH(3), CH(2)NH(2), and CO(2). Whereas Amt/MEP proteins, are agreed to transport ammonia (NH(3)/NH(4)(+)), the primary substrate, for Rh proteins has been controversial. Initial studies suggested that Rh, proteins also transport ammonia, but more recent evidence suggests that, they transport CO(2). Here we report the first structure of an Rh family, member, the Rh protein from the chemolithoautotrophic ammonia-oxidizing, bacterium Nitrosomonas europaea. This Rh protein exhibits a number of, similarities to its Amt cousins, including a trimeric oligomeric state, a, central pore with an unusual twin-His site in the middle, and a Phe, residue that blocks the channel for small-molecule transport. However, there are some significant differences, the most notable being the, presence of an additional cytoplasmic C-terminal alpha-helix, an increased, number of internal proline residues along the transmembrane helices, and a, specific set of residues that appear to link the C-terminal helix to Phe, blockage. This latter linkage suggests a mechanism in which binding of a, partner protein to the C terminus could regulate channel opening. Another, difference is the absence of the extracellular pi-cation binding site, conserved in Amt/Mep structures. Instead, CO(2) pressurization experiments, identify a CO(2) binding site near the intracellular exit of the channel, whose residues are highly conserved in all Rh proteins, except those, belonging to the Rh30 subfamily. The implications of these findings on the, functional role of the human Rh antigens are discussed.
About this Structure
3B9Y is a Single protein structure of sequence from Nitrosomonas europaea atcc 19718 with and as ligands. Full crystallographic information is available from OCA.
Reference
Structure of the Nitrosomonas europaea Rh protein., Li X, Jayachandran S, Nguyen HH, Chan MK, Proc Natl Acad Sci U S A. 2007 Dec 4;104(49):19279-84. Epub 2007 Nov 26. PMID:18040042
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