Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 10, Pages 2990-2995Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1423672112
Keywords
microcompartment; protein channel; carboxysome; Salmonella; B-12
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Funding
- National Center for Research Resources Grant [5P41RR015301-10]
- National Institute of General Medical Sciences Grant from NIH [8 P41 GM103403-10]
- NIH [R01AI081146]
- Biological and Environmental Research program of the Department of Energy (DOE) Office of Science
- Chemistry-Biology Interface NIH Training Grant [T32-GM008496]
- University of California, Los Angeles Graduate Division
- DOE [DE-AC02-06CH11357]
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Bacterial microcompartments are widespread prokaryotic organelles that have important and diverse roles ranging from carbon fixation to enteric pathogenesis. Current models for microcompartment function propose that their outer protein shell is selectively permeable to small molecules, but whether a protein shell can mediate selective permeability and how this occurs are unresolved questions. Here, biochemical and physiological studies of structure-guided mutants are used to show that the hexameric PduA shell protein of the 1,2-propanediol utilization (Pdu) microcompartment forms a selectively permeable pore tailored for the influx of 1,2-propanediol (the substrate of the Pdu microcompartment) while restricting the efflux of propionaldehyde, a toxic intermediate of 1,2-propanediol catabolism. Crystal structures of various PduA mutants provide a foundation for interpreting the observed biochemical and phenotypic data in terms of molecular diffusion across the shell. Overall, these studies provide a basis for understanding a class of selectively permeable channels formed by nonmembrane proteins.
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