Georgios Skiniotis, Postdoctoral Faculty Sponsor
Plastic structures for diverse substrates: A revisit of human ABC transporters
PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS
2022; 90 (10): 1749-1765
ATP-binding cassette (ABC) superfamily is one of the largest groups of primary active transporters that could be found in all kingdoms of life from bacteria to humans. In humans, ABC transporters can selectively transport a wide spectrum of substrates across membranes, thus playing a pivotal role in multiple physiological processes. In addition, due to the ability of exporting clinic therapeutics, some ABC transporters were originally termed multidrug resistance proteins. Increasing investigations of human ABC transporters in recent years have provided abundant information for elucidating their structural features, based on the structures at distinct states in a transport cycle. This review focuses on the recent progress in human ABC structural analyses, substrate binding specificities, and translocation mechanisms. We dedicate to summarize the common features of human ABC transporters in different subfamilies, and to discuss the possibility to apply the fast-developing techniques, such as cryogenic electron microscopy, and artificial intelligence-assisted structure prediction, for future studies.
View details for DOI 10.1002/prot.26406
View details for Web of Science ID 000844709700001
View details for PubMedID 35924777
Structural basis of substrate recognition and translocation by human very long-chain fatty acid transporter ABCD1.
2022; 13 (1): 3299
Human ABC transporter ABCD1 transports very long-chain fatty acids from cytosol to peroxisome for β-oxidation, dysfunction of which usually causes the X-linked adrenoleukodystrophy (X-ALD). Here, we report three cryogenic electron microscopy structures of ABCD1: the apo-form, substrate- and ATP-bound forms. Distinct from what was seen in the previously reported ABC transporters, the two symmetric molecules of behenoyl coenzyme A (C22:0-CoA) cooperatively bind to the transmembrane domains (TMDs). For each C22:0-CoA, the hydrophilic 3'-phospho-ADP moiety of CoA portion inserts into one TMD, with the succeeding pantothenate and cysteamine moiety crossing the inter-domain cavity, whereas the hydrophobic fatty acyl chain extends to the opposite TMD. Structural analysis combined with biochemical assays illustrates snapshots of ABCD1-mediated substrate transport cycle. It advances our understanding on the selective oxidation of fatty acids and molecular pathology of X-ALD.
View details for DOI 10.1038/s41467-022-30974-5
View details for PubMedID 35676282
Structure and transport mechanism of the human cholesterol transporter ABCG1
2022; 38 (4): 110298
The reverse cholesterol transport pathway is responsible for the maintenance of human cholesterol homeostasis, an imbalance of which usually leads to atherosclerosis. As a key component of this pathway, the ATP-binding cassette transporter ABCG1 forwards cellular cholesterol to the extracellular acceptor nascent high-density lipoprotein (HDL). Here, we report a 3.26-Å cryo-electron microscopy structure of cholesterol-bound ABCG1 in an inward-facing conformation, which represents a turnover condition upon ATP binding. Structural analyses combined with functional assays reveals that a cluster of conserved hydrophobic residues, in addition to two sphingomyelins, constitute a well-defined cholesterol-binding cavity. The exit of this cavity is closed by three pairs of conserved Phe residues, which constitute a hydrophobic path for the release of cholesterol in an acceptor concentration-dependent manner. Overall, we propose an ABCG1-driven cholesterol transport cycle initiated by sphingomyelin-assisted cholesterol recruitment and accomplished by the release of cholesterol to HDL.
View details for DOI 10.1016/j.celrep.2022.110298
View details for Web of Science ID 000750976000008
View details for PubMedID 35081353
- Structures of human bile acid exporter ABCB11 reveal a transport mechanism facilitated by two tandem substrate-binding pockets CELL RESEARCH 2022; 32 (5): 501-504
A gain-of-function mutation of the MATE family transporter DTX6 confers paraquat resistance in Arabidopsis
2021; 14 (12): 2126-2133
Paraquat is one of the most widely used nonselective herbicides and has elicited the emergence of paraquat-resistant weeds. However, the molecular mechanisms of paraquat resistance are not completely understood. Here we report the Arabidopsis gain-of-function mutant pqt15-D with significantly enhanced resistance to paraquat and the corresponding gene PQT15, which encodes the Multidrug and Toxic Extrusion (MATE) transporter DTX6. A point mutation at +932 bp in DTX6 causes a G311E amino acid substitution, enhancing the paraquat resistance of pqt15-D, and overexpression of DTX6/PQT15 in the wild-type plants also results in strong paraquat resistance. Moreover, heterologous expression of DTX6 and DTX6-D in Escherichia coli significantly enhances bacterial resistance to paraquat. Importantly, overexpression of DTX6-D enables Arabidopsis plants to tolerate 4 mM paraquat, a near-commercial application level. DTX6/PQT15 is localized in the plasma membrane and endomembrane, and functions as a paraquat efflux transporter as demonstrated by paraquat efflux assays with isolated protoplasts and bacterial cells. Taken together, our results demonstrate that DTX6/PQT15 is an efflux transporter that confers paraquat resistance by exporting paraquat out of the cytosol. These findings reveal a molecular mechanism of paraquat resistance in higher plants and provide a promising candidate gene for engineering paraquat-resistant crops.
View details for DOI 10.1016/j.molp.2021.09.004
View details for Web of Science ID 000729175700017
View details for PubMedID 34509638
- Structures of cyanobacterial bicarbonate transporter SbtA and its complex with PII-like SbtB CELL DISCOVERY 2021; 7 (1): 63
- Cryo-EM structure of human bile salts exporter ABCB11 CELL RESEARCH 2020; 30 (7): 623-625
- Cryo-EM structure of human lysosomal cobalamin exporter ABCD4 CELL RESEARCH 2019; 29 (12): 1039-1041