An integrated transport mechanism of the maltose ABC importer

• Published in: Research in microbiology Vol. 170; no. 8; pp. 321 - 337
• Main Authors: Mächtel, Rebecca, Narducci, Alessandra, Griffith, Douglas A., Cordes, Thorben, Orelle, Cédric
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01.11.2019; Elsevier
• Subjects: ABC transporter; Adenosine Triphosphate - metabolism; ATP-Binding Cassette Transporters - metabolism; Binding Sites; Biochemistry, Molecular Biology; Biological Transport - physiology; Cell Membrane - metabolism; EPR spectroscopy; Escherichia coli - metabolism; Escherichia coli Proteins - metabolism; Importer; Life Sciences; Maltose - metabolism; Models, Molecular; Periplasmic Binding Proteins - metabolism; Polysaccharides - metabolism; Protein Conformation; Single molecule fluorescence; smFRET; Substrate-binding protein; Single molecule fluorescence; smFRET; Substrate-binding protein; ABC transporter; EPR spectroscopy; Importer
• ISSN: 0923-2508; 1769-7123; 1769-7123; 0923-2508
• DOI: 10.1016/j.resmic.2019.09.004

ATP-binding cassette (ABC) transporters use the energy of ATP hydrolysis to transport a large diversity of molecules actively across biological membranes. A combination of biochemical, biophysical, and structural studies has established the maltose transporter MalFGK2 as one of the best characterized proteins of the ABC family. MalF and MalG are the transmembrane domains, and two MalKs form a homodimer of nucleotide-binding domains. A periplasmic maltose-binding protein (MalE) delivers maltose and other maltodextrins to the transporter, and triggers its ATPase activity. Substrate import occurs in a unidirectional manner by ATP-driven conformational changes in MalK2 that allow alternating access of the substrate-binding site in MalF to each side of the membrane. In this review, we present an integrated molecular mechanism of the transport process considering all currently available information. Furthermore, we summarize remaining inconsistencies and outline possible future routes to decipher the full mechanistic details of transport by MalEFGK2 complex and that of related importer systems.