THE STRUCTURE OF THE CYTOPLASMIC MEMBRANE COMPONENTS OF THE RIBOSE HIGH AFFINITY TRANSPORT SYSTEM OF ESCHERICHIA COLI K12 (PROTEIN, DNA SEQUENCE)
Abstract
The ribose high affinity transport system of Escherichia coli K12 requires the expression of at least four genes, rbsD, rbsA, rbsC and rbsB. The rbsB gene encodes the periplasmic ribose binding protein while the rbsD, rbsA and rbsC genes encode components which are likely to be located on or in the cytoplasmic membrane. At this time available evidence indicates that these four proteins constitute the entire high affinity transport system for ribose. The rbsC gene encodes a protein of 321 amino acids, and the sequence is characteristic of integral membrane proteins. The calculated molecular weight of this protein is 33,398. The rbsA gene encodes a protein of 501 amino acids that has about 25% charged residues. The rbsA protein shows striking homology to the proteins encoded by the hisP, malK, pstB and oppD genes. These proteins also have features common to a number of proteins that bind nucleotides, and this may suggest that these proteins are involved in energy coupling. The rbsA structural gene has been cloned downstream from the lambda P(,L) promoter, and upon induction rbsA protein can be expressed to about 15% of the cellular protein. The protein has been purified to near homogeneity, the first report of a purification of a cytoplasmic membrane component of a transport system. The amino acid composition and amino terminal sequence is consistent with the predicted sequence. Purified rbsA protein binds ATP.
Degree
Ph.D.
Subject Area
Biochemistry
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