7n59 | pdb_00007n59
Structure of AtAtm3 in the inward-facing conformation with GSSG bound
Structural highlights
Function[AB25B_ARATH] Performs an essential function in the generation of cytoplasmic iron-sulfur proteins by mediating export of Fe/S cluster precursors synthesized by NFS1 and other mitochondrial proteins. Not required for mitochondrial and plastid Fe-S enzymes. Probably involved in the export of cyclic pyranopterin monophosphate (cPMP) from mitochondria into the cytosol. Mediates glutathione-dependent resistance to heavy metals such as cadmium and lead, as well as their transport from roots to leaves. Regulates nonprotein thiols (NPSH) and the cellular level of glutathione (GSH).[1] [2] [3] [4] [5] Publication Abstract from PubMedThe ATP binding cassette (ABC) transporter of mitochondria (Atm) from Arabidopsis thaliana (AtAtm3) has been implicated in the maturation of cytosolic iron-sulfur proteins and heavy metal detoxification, plausibly by exporting glutathione derivatives. Using single-particle cryo-electron microscopy, we have determined four structures of AtAtm3 in three different conformational states: two inward-facing conformations (with and without bound oxidized glutathione [GSSG]), together with closed and outward-facing states stabilized by MgADP-VO4. These structures not only provide a structural framework for defining the alternating access transport cycle, but also reveal the paucity of cysteine residues in the glutathione binding site that could potentially form inhibitory mixed disulfides with GSSG. Despite extensive efforts, we were unable to prepare the ternary complex of AtAtm3 containing both GSSG and MgATP. A survey of structurally characterized type IV ABC transporters that includes AtAtm3 establishes that while nucleotides are found associated with all conformational states, they are effectively required to stabilize occluded, closed, and outward-facing conformations. In contrast, transport substrates have only been observed associated with inward-facing conformations. The absence of structures with dimerized nucleotide binding domains containing both nucleotide and transport substrate suggests that this form of the ternary complex exists only transiently during the transport cycle. Glutathione binding to the plant AtAtm3 transporter and implications for the conformational coupling of ABC transporters.,Fan C, Rees DC Elife. 2022 Mar 25;11. pii: 76140. doi: 10.7554/eLife.76140. PMID:35333177[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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