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A sugar‐specific porin, ScrY, is involved in sucrose uptake in enteric bacteria
Author(s) -
Schmid K.,
Ebner R.,
Jahreis K.,
Lengeler J. W.,
Titgemeyer F.
Publication year - 1991
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.1365-2958.1991.tb00769.x
Subject(s) - biology , porin , pep group translocation , biochemistry , mutant , bacterial outer membrane , fructose , sucrose , enterobacteriaceae , bacteria , microbiology and biotechnology , escherichia coli , gene , genetics
Summary During the molecular analysis of a plasmid‐coded sucrose metabolic pathway of enteric bacteria, a gene, scrY, was found whose product, ScrY, had all the properties of a bacterial porin (Schmid et al , 1988). Loss of this protein (M r 58kDa), localized in the outer membrane, led, as shown here, to an increase in the apparent K m for sucrose transport in whole cells from 10 μ M in wild‐type cells to 300 μ M in mutant cells. This contrasts with the K m for sucrose phosphorylation as measured in membrane vesicles from mutant and wild‐type cells, which remained unchanged at about 10 μ M, and reflects the activity of the sucrose‐specific Enzymell of the phosphoenolpyruvate‐dependent carbohydrate:phosphotransferase system (PTS) responsible for uptake through the inner membrane. Furthermore, the presence of ScrY restored growth on maltodextrins in cells devoid of LamB, thus complementing the lack of this maltoporin. The amino acid sequence deduced from the DNA sequence was determined for the plasmid‐coded and the ScrY porin coded in the chromosome of Klebsiella pneumoniae. Both show high identity (86%) to each other, and to the channel domain of LamB, further corroborating the conclusion that they constitute porins.