Article

Crystal structure of glycerophosphodiester phosphodiesterase from Agrobacterium tumefaciens by SAD with a large asymmetric unit

Biology Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Proteins Structure Function and Bioinformatics (Impact Factor: 3.34). 11/2006; 65(2):514-8. DOI: 10.1002/prot.21079
Source: PubMed
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    ABSTRACT: periplasmic glycerophosphodiester phosphodiesterase, GlpQ. UgpQ has broad substrate specificity toward various glycerophosphodiesters, producing sn-glycerol-3-phosphate and the corresponding alcohols. UgpQ accumulates under conditions of phosphate starvation, suggesting that it allows the utilization of glycerophos- phodiesters as a source of phosphate. These results clarify how E. coli utilizes glycerophosphodiesters using two homologous enzymes, UgpQ and GlpQ. Glycerophosphodiesters are enzymatically produced by phospholipases A1 and A2 from membrane phospholipids (10, 25). There are several glycerophosphodiesters, based on the alcohol moiety: glycerophosphocholine (GPC), glycerophos- phoethanolamine (GPE), glycerophosphoinositol (GPI), glyc- erophosphoserine (GPS), glycerophosphoglycerol (GPG), and so on. Glycerophosphodiesters are further degraded by glyc- erophosphodiester phosphodiesterase (EC 3.1.4.46), produc- ing the corresponding alcohols and sn-glycerol-3-phosphate (G3P), which is an essential precursor for de novo synthesis of glycerophospholipids. In the metabolic pathway of Escherichia coli, glycerophosphodiesters are thought to be utilized by two distinct systems. One is the Glp system, and the other is the Ugp system (26). In each system, related proteins are encoded by one or more operons. They contain genes that code for transporter proteins and enzymes. The glpTQ operon simultaneously regulates the transcrip- tion of related genes (13). GlpT, an ABC transporter, actively transports G3P from the periplasm into the cytosol through the plasma membrane. glpQ codes for a periplasmic glycerophos- phodiester phosphodiesterase. GlpQ processes periplasmic glycerophosphodiesters into G3P and corresponding alcohols (14). The other glycerophosphodiester-utilizing system is the Ugp system. The ugp operon is constituted of ugpB, ugpA, ugpE, ugpC, and ugpQ (4, 19). UgpB specifically binds to glycero- phosphodiesters and delivers them to the membrane trans- porter. UgpA, UgpE, and UgpC constitute the transporter for glycerophosphodiesters. UgpQ, a 27-kDa protein, is a cytosolic glycerophosphodiester phosphodiesterase and is homologous to GlpQ.