A new family of cyanobacterial penicillin-binding proteins. A missing link in the evolution of class A beta-lactamases.
It is largely accepted that serine beta-lactamases evolved from some ancestral DD-peptidases involved in the biosynthesis and maintenance of the bacterial peptidoglycan. DD-peptidases are also called penicillin-binding proteins (PBPs), since they form stable acyl-enzymes with beta-lactam antibiotics, such as penicillins. On the other hand, beta-lactamases react similarly with these antibiotics, but the acyl-enzymes are unstable and rapidly hydrolyzed. Besides, all known PBPs and beta-lactamases share very low sequence similarities, thus rendering it difficult to understand how a PBP could evolve into a beta-lactamase. In this study, we identified a new family of cyanobacterial PBPs featuring the highest sequence similarity with the most widespread class A beta-lactamases. Interestingly, the Omega-loop, which, in the beta-lactamases, carries an essential glutamate involved in the deacylation process, is six amino acids shorter and does not contain any glutamate residue. From this new family of proteins, we characterized PBP-A from Thermosynechococcus elongatus and discovered hydrolytic activity with synthetic thiolesters that are usually good substrates of DD-peptidases. Penicillin degradation pathways as well as acylation and deacylation rates are characteristic of PBPs. In a first attempt to generate beta-lactamase activity, a 90-fold increase in deacylation rate was obtained by introducing a glutamate in the shorter Omega-loop.
Urbach
Carole
C
Laboratoire d'Ingénierie des Protéines et des Peptides, Institut des Sciences de la Vie, Université Catholique de Louvain, Place Croix du Sud 4-5, bte3, 1348 Louvain la-Neuve, Belgium.
Fastrez
Jacques
J
Soumillion
Patrice
P
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics*; D018698:Glutamic Acid / Q000737:chemistry; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D046915:Penicillin-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D046940:Synechococcus / Q000235:genetics; D001618:beta-Lactamases / Q000378:metabolism*
D046915:Penicillin-Binding Proteins; D010455:Peptides; D018698:Glutamic Acid; D001618:beta-Lactamases