5a4x
The crystal structure of Arabidopsis thaliana CAR4 in complex with two calcium ions and Zn
Structural highlights
FunctionCAR4_ARATH Mediates the transient calcium-dependent interaction of PYR/PYL/RCAR abscisic acid (ABA) receptors with the plasma membrane and thus regulates ABA sensitivity (PubMed:26719420, PubMed:25465408). Stimulates the GTPase/ATPase activities of YchF1, and regulates its subcellular localization. Promotes tolerance towards salinity stress by limiting the accumulation of reactive oxygen species (ROS) (PubMed:23550829). Promotes resistance to bacterial pathogens (e.g. Xanthomonas oryzae pv. oryzae and P. syringae pv. tomato DC3000) (By similarity). Binds liposomes in the absence of exogenous Ca(2+), but this activity is enhanced in the presence of Ca(2+) and generates membrane curvature (PubMed:26719420).[UniProtKB:Q6YWF1][1] [2] [3] Publication Abstract from PubMedRegulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca(2+) are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca(2+) signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca(2+)-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca(2+) sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca(2+)-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress. Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling.,Diaz M, Sanchez-Barrena MJ, Gonzalez-Rubio JM, Rodriguez L, Fernandez D, Antoni R, Yunta C, Belda-Palazon B, Gonzalez-Guzman M, Peirats-Llobet M, Menendez M, Boskovic J, Marquez JA, Rodriguez PL, Albert A Proc Natl Acad Sci U S A. 2016 Jan 19;113(3):E396-405. doi:, 10.1073/pnas.1512779113. Epub 2015 Dec 30. PMID:26719420[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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