Structural and functional characterization of OmpF porin mutants selected for larger pore size. I. Crystallographic analysis.
OmpF porin is a nonspecific pore protein from the outer membrane of Escherichia coli. Previously, a set of mutants was selected that allow the passage of long maltodextrins that do not translocate through the wild-type pore. Here, we describe the crystal structures of four point mutants and one deletion mutant from this set; their functional characterization is reported in the accompanying paper (Saint, N., Lou, K.-L., Widmer, C., Luckey, M., Schirmer, T., Rosenbusch, J. P. (1996) J. Biol. Chem. 271, 20676-20680). All mutations have a local effect on the structure of the pore constriction and result in a larger pore cross-section. Substitution of each of the three closely packed arginine residues at the pore constriction (Arg-42, Arg-82, and Arg-132) by shorter uncharged residues causes rearrangement of the adjacent basic residues. This demonstrates mutual stabilization of these residues in the wild-type porin. Deletion of six residues from the internal loop (Delta109-114) results in disorder of seven adjacent residues but does not alter the structure of the beta-barrel framework. Thus, the large hollow beta-barrel motif can be regarded as an autonomous structure.
Lou
K L
KL
Department of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Saint
N
N
Prilipov
A
A
Rummel
G
G
Benson
S A
SA
Rosenbusch
J P
JP
Schirmer
T
T
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D018360:Crystallography, X-Ray; D017931:DNA Primers / Q000737:chemistry; D004926:Escherichia coli; D006860:Hydrogen Bonding; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
D001425:Bacterial Outer Membrane Proteins; D017931:DNA Primers; D007473:Ion Channels