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The periplasmic membrane proximal domain of MacA acts as a switch in stimulation of ATP hydrolysis by MacB transporter
Author(s) -
Modali Sita D.,
Zgurskaya Helen I.
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07744.x
Subject(s) - periplasmic space , bacterial outer membrane , atp hydrolysis , transporter , escherichia coli , biology , biochemistry , membrane transport protein , microbiology and biotechnology , membrane protein , atpase , membrane , enzyme , gene
Summary Escherichia coli MacAB‐TolC is a tripartite macrolide efflux transporter driven by hydrolysis of ATP. In this complex, MacA is the periplasmic membrane fusion protein that stimulates the activity of MacB transporter and establishes the link with the outer membrane channel TolC. The molecular mechanism by which MacA stimulates MacB remains unknown. Here, we report that the periplasmic membrane proximal domain of MacA plays a critical role in functional MacA–MacB interactions and stimulation of MacB ATPase activity. Binding of MacA to MacB stabilizes the ATP‐bound conformation of MacB, whereas interactions with both MacB and TolC affect the conformation of MacA. A single G353A substitution in the C‐terminus of MacA inactivates MacAB‐TolC function by changing the conformation of the membrane proximal domain of MacA and disrupting the proper assembly of the MacA‐MacB complex. We propose that MacA acts in transport by promoting MacB transition into the closed ATP‐bound conformation and in this respect, is similar to the periplasmic solute‐binding proteins.