Poster: Water relations
Abs #
161: Structure, function and regulation of two subgroups of the Nodulin 26-like Intrinsic Protein family of aquaglyceroporins
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Presenter: |
Wallace, Ian S, iwallace@utk.edu |
Authors | Wallace, Ian S (A) Guenther, James F (A) Roberts, Daniel M (A) | | Affiliations: |
(A): The University of Tennessee, Knoxville
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The Nodulin 26-like Instrinsic Protein (NIP) family is a subfamily of the Major Intrinsic Protein (MIP) superfamily with structural similarity to soybean nodulin 26. NIPs are multifunctional transporters that mediate the bidirectional flux of water, glycerol, NH3, and other small solutes across cellular membranes. The nine NIP genes of Arabidopsis thaliana have been organized into two subgroups based on homology modeling of the pore selectivity region (the ar/R region). The NIP I subgroup (NIP1;1, NIP1;2, NIP2;1, NIP3;1, NIP4;1, NIP4;2) share higher similarity with nodulin 26, and appear to form aquaglyceroporin transporters, and many have a conserved CDPK phosphorylation site at the carboxyl terminus. Phosphorylation of soybean nodulin 26 is stimulated in response to water deficit, resulting in enhanced transport activity. Additionally, interacting proteins that recognize the carboxyl terminal region of nodulin 26 have been identified, suggesting that NIP I proteins may possess a binding epitope for interacting proteins that could further modulate their function. In contrast, the NIP II subgroup (NIP5;1, NIP6;1, NIP7;1) differs in sequence at the ar/R and NPA pore regions and lacks the conserved CDPK phosphorylation site. Functional analysis of NIP6;1 shows that it is a glyceroporin with an unusually low water permeability. The amino and carboxyl terminal regions of NIP5;1, 6;1 and 7;1 also show consensus phosphorylation sequences for MAP kinases (P-X-S-P). These data suggest that the NIP subfamily can be divided into two structurally and functionally distinct groups with different transport selectivity and potentially distinct regulatory properties. (Supported by an ASPB SURF award to ISW and by NSF grant MCB-0237219)
