3BUZ

Crystal structure of ia-bTAD-actin complex

Summary for 3BUZ

• Entry DOI: 10.2210/pdb3buz/pdb
• Descriptor: Iota toxin component Ia, Actin, alpha skeletal muscle, BETA-METHYLENE-THIAZOLE-4-CARBOXYAMIDE-ADENINE DINUCLEOTIDE, ... (7 entities in total)
• Functional Keywords: iota toxin, actin, toxin-actin complex, acetylation, atp-binding, cytoplasm, cytoskeleton, methylation, muscle protein, nucleotide-binding, structural protein, toxin-structural protein complex, toxin/structural protein
• Biological source: Clostridium perfringens; More
• Cellular location: Cytoplasm, cytoskeleton: P68135
• Total number of polymer chains: 2
• Total formula weight: 91147.42

Authors

Tsuge, H.,Nagahama, M.,Oda, M.,Iwamoto, S.,Utsunomiya, H.,Marquez, V.E.,Katunuma, N.,Nishizawa, M.,Sakurai, J. (deposition date: 2008-01-04, release date: 2008-05-13, Last modification date: 2023-11-01)

Primary citation

Tsuge, H.,Nagahama, M.,Oda, M.,Iwamoto, S.,Utsunomiya, H.,Marquez, V.E.,Katunuma, N.,Nishizawa, M.,Sakurai, J.
Structural basis of actin recognition and arginine ADP-ribosylation by Clostridium perfringens iota-toxin
Proc.Natl.Acad.Sci.Usa, 105:7399-7404, 2008

PubMed Abstract: The ADP-ribosylating toxins (ADPRTs) produced by pathogenic bacteria modify intracellular protein and affect eukaryotic cell function. Actin-specific ADPRTs (including Clostridium perfringens iota-toxin and Clostridium botulinum C2 toxin) ADP-ribosylate G-actin at Arg-177, leading to disorganization of the cytoskeleton and cell death. Although the structures of many actin-specific ADPRTs are available, the mechanisms underlying actin recognition and selective ADP-ribosylation of Arg-177 remain unknown. Here we report the crystal structure of actin-Ia in complex with the nonhydrolyzable NAD analog betaTAD at 2.8 A resolution. The structure indicates that Ia recognizes actin via five loops around NAD: loop I (Tyr-60-Tyr-62 in the N domain), loop II (active-site loop), loop III, loop IV (PN loop), and loop V (ADP-ribosylating turn-turn loop). We used site-directed mutagenesis to confirm that loop I on the N domain and loop II are essential for the ADP-ribosyltransferase activity. Furthermore, we revealed that Glu-378 on the EXE loop is in close proximity to Arg-177 in actin, and we proposed that the ADP-ribosylation of Arg-177 proceeds by an SN1 reaction via first an oxocarbenium ion intermediate and second a cationic intermediate by alleviating the strained conformation of the first oxocarbenium ion. Our results suggest a common reaction mechanism for ADPRTs. Moreover, the structure might be of use in rational drug design to block toxin-substrate recognition.

PubMed: 18490658
DOI: 10.1073/pnas.0801215105

Experimental method

X-RAY DIFFRACTION (2.81 Å)