Co-Regulation in Escherichia coli of a Novel Transport System for sn -Glycerol-3-Phosphate and Outer Membrane Protein Ic (e, E) with Alkaline Phosphatase and Phosphate-Binding Protein

Abstract

Mutants constitutive for the novel outer membrane protein Ic (e or E) contained a recently discovered binding protein for sn-glycerol-3-phosphate. The corresponding parental strains missing the outer membrane protein Ic (e, E) were negative or strongly reduced in the synthesis of the binding protein. In addition, strains that were previously isolated as mutants constitutive for the sn-glycerol-3-phosphate transport system (ugp+ mutants) and that produced the novel periplasmic proteins GP1 to GP4 also synthesized a new outer membrane protein with the same electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels as protein Ic. Screening of different ugp+ mutants revealed the existence of three types in respect to the four novel periplasmic proteins GP1, -2, -3, and -4: (i) one containing all four proteins; (ii) one containing only proteins GP1, -2, and -3; (iii) one containing only proteins GP1, -2, and -4. In confirmation of the data presented in the accompanying paper by Tommassen and Lugtenberg (J. Bacteriol. 143:151-157, 1980), we found that purified GP1 is identical to alkaline phosphatase, whereas purified GP3 has binding activity of inorganic phosphate and is identical to the phosphate-binding protein. Moreover, growth conditions that lead in a wild-type strain to the derepression of alkaline phosphatase synthesis also derepressed the synthesis of the sn-glycerol-3-phosphate-binding protein as well as the corresponding transport system. Thus, the new sn-glycerol-3-phosphate transport system is part of the alkaline phosphatase regulatory system.Recently, we found a new transport system for sn-glycerol-3-phosphate (G3P) in mutants (ugp+ mutants) that arose as G3P+ suppressors in strains carrying a defective transport system for G3P coded for by gipT (3) at 48 min on the Escherichia coli chromosome (4). These ugp+ mutants mapped outside gipT and synthesized the new periplasmic proteins (GP1, -2, and -3). One of these proteins (GP2) was identified as a high-affinity binding protein for G3P (2).Along other lines, we were interested in the pore-forning activity of osmotic shock fluid in black lipid films due to soluble outer membrane proteins Ia and lb (6). In this respect, we were interested whether or not the newly discovered outer membrane protein Ic (18) also exhibited pore-forming activity when shock fluids of this mutant were used in the black lipid pore assay. Although this was indeed the case (R. Benz and U. Henning, manuscript in preparation) we noticed that the periplasmic proteins of the Iccarrying strain exhibited a polyacrylamide gel pattern very similar to those obtained from shock fluids of our G3P+ ugp+ mutants. 142

The ugp-encoded glycerophosphoryldiester phosphodiesterase, a transport-related enzyme of Escherichia coli

“…For the maximal expression of U gp the cells have to be induced by phosphate starvation or mutants have to be used that are expressing the pho regulon constitutively (phoR or pst). The observation that mutations in phoB as well as double mutants in phoR and phoM prevent expression, identify the U gp transport system as a member of the pho regulon [4,21]. The apparent K m of uptake of Ugp for its major substrate G3P is around 2 ILM, thus the Ugp system has about a lO-fold higher affinity for G3P than the GlpT system [18].…”

“…In this experiment, for technical reasons (low specific radioactivity), the substrate concentration had to be much higher. As a result, GPE in the medium disappears only slowly and from the internal G3P only traces of lipid pre-ugp+ phoB ugp" on multicop y plasmid ugpB Genotype Table 2 Binding of e 4 cursors are being formed. Similar data were obtained with [14C]glycerophosphorylglycerol (GPG) labeled in both glycerol molecules of GPG (Fig.…”

“…However, simultaneously with the appearance of constitutive alkaline phosphatase a second transport system for G3P and glycerol phosphoryl diesters such as glycerophosphorylethanolarnine (GPE), is synthesized, the Ugp system (uptake glycerol phosphate) [4][5][6].…”

Nucleotide sequence of the ugp genes of Escherichia coli K‐12: homology to the maltose system

“…1985;Ambudkar et ai, 1986). The synthesis of the Ugp system, which is a periplasmic binding protein (BP)-dependent uptake system, is induoed when cells are starved of P, (Argast and Boos, 1980). A genetic analysis of the cloned ugp genes suggested the existence of two separate operons which comprise at least four genes: ugpD and ugpB constitute one operon, and ugpA and ugpC the other (Schweizer and Boos, 1984).…”

Expression and regulation of protein K, an Escherichia coli K1 porin, in Escherichia coli K‐12

“…The E coli K-12 cell can also produce other porin proteins. For example, when the cell is starved for phosphate, the PhoE porin protein is induced [5,6]. lc protein is a porin that is expressed when an E coli cell is lysogenized with phage PA-2 [7].…”