Specificity determinants for the two tRNA substrates of the cyclodipeptide synthase AlbC from Streptomyces noursei.
Cyclodipeptide synthases (CDPSs) use two aminoacyl-tRNA substrates in a sequential ping-pong mechanism to form a cyclodipeptide. The crystal structures of three CDPSs have been determined and all show a Rossmann-fold domain similar to the catalytic domain of class-I aminoacyl-tRNA synthetases (aaRSs). Structural features and mutational analyses however suggest that CDPSs and aaRSs interact differently with their tRNA substrates. We used AlbC from Streptomyces noursei that mainly produces cyclo(l-Phe-l-Leu) to investigate the interaction of a CDPS with its substrates. We demonstrate that Phe-tRNA(Phe) is the first substrate accommodated by AlbC. Its binding to AlbC is dependent on basic residues located in the helix α4 that form a basic patch at the surface of the protein. AlbC does not use all of the Leu-tRNA(Leu) isoacceptors as a second substrate. We show that the G(1)-C(72) pair of the acceptor stem is essential for the recognition of the second substrate. Substitution of D163 located in the loop α6-α7 or D205 located in the loop β6-α8 affected Leu-tRNA(Leu) isoacceptors specificity, suggesting the involvement of these residues in the binding of the second substrate. This is the first demonstration that the two substrates of CDPSs are accommodated in different binding sites.
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France mireille.moutiez@cea.fr.
Mireille
M
Moutiez
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France.
Jérôme
J
Seguin
INSERM, U1138, LRMA, Equipe 12 du Centre de Recherche des Cordeliers, Paris 75006, France Université Pierre et Marie Curie, UMR S 1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR S 1138, Paris, France.
Matthieu
M
Fonvielle
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France.
Pascal
P
Belin
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France.
Isabelle Béatrice
IB
Jacques
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France.
Emmanuel
E
Favry
INSERM, U1138, LRMA, Equipe 12 du Centre de Recherche des Cordeliers, Paris 75006, France Université Pierre et Marie Curie, UMR S 1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR S 1138, Paris, France.
Michel
M
Arthur
Service d'Ingénierie Moléculaire des Protéines, iBiTec-S, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 91191 Gif-sur-Yvette Cedex, France mireille.moutiez@cea.fr.
Muriel
M
Gondry
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D010453:Peptide Synthases / Q000737:chemistry / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism*; D012356:RNA, Transfer, Leu / Q000737:chemistry / Q000378:metabolism; D012360:RNA, Transfer, Phe / Q000737:chemistry / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology*; D013379:Substrate Specificity
D001426:Bacterial Proteins; D012346:RNA, Transfer, Amino Acyl; D012356:RNA, Transfer, Leu; D012360:RNA, Transfer, Phe; D010453:Peptide Synthases