3ITW

Crystal structure of TioX from Micromonospora sp. ML1

Summary for 3ITW

• Entry DOI: 10.2210/pdb3itw/pdb
• Descriptor: Protein tioX (2 entities in total)
• Functional Keywords: bleomycin resistance fold, bisintercalator, solvent-exposed trp residue, thiocoraline, protein binding, peptide binding protein
• Biological source: Micromonospora sp. ML1
• Total number of polymer chains: 2
• Total formula weight: 30941.36

Authors

Biswas, T.,Garneau-Tsodikova, S.,Tsodikov, O.V. (deposition date: 2009-08-28, release date: 2010-02-16, Last modification date: 2011-07-13)

Primary citation

Biswas, T.,Zolova, O.E.,Lombo, F.,de la Calle, F.,Salas, J.A.,Tsodikov, O.V.,Garneau-Tsodikova, S.
A New Scaffold of an Old Protein Fold Ensures Binding to the Bisintercalator Thiocoraline.
J.Mol.Biol., 397:495-507, 2010

PubMed Abstract: Thiocoraline is a thiodepsipeptide with potent antitumor activity. TioX, a protein with an unidentified function, is encoded by a gene of the thiocoraline biosynthetic gene cluster. The crystal structure of the full-length TioX protein at 2.15 A resolution reveals that TioX protomer shares an ancient betaalphabetabetabeta fold motif with glyoxalase I and bleomycin resistance protein families, despite a very low sequence homology. Intriguingly, four TioX monomers form a unique 2-fold symmetric tetrameric assembly that is stabilized by four intermolecular disulfide bonds formed cyclically between Cys60 and Cys66 of adjacent monomers. The arrangement of two of the four monomers in the TioX tetramer is analogous to that in dimeric bleomycin resistance proteins. This analogy indicates that this novel higher-order structural scaffold of TioX may have evolved to bind thiocoraline. Our equilibrium titration studies demonstrate the binding of a thiocoraline chromophore analog, quinaldic acid, to TioX, thereby substantiating this model. Furthermore, a strain of Streptomyces albus containing an exogenous thiocoraline gene cluster devoid of functional tioX maintains thiocoraline production, albeit with a lower yield. Taken together, these observations rule out a direct enzymatic function of TioX and suggest that TioX is involved in thiocoraline resistance or secretion.

PubMed: 20122935
DOI: 10.1016/j.jmb.2010.01.053

Experimental method

X-RAY DIFFRACTION (2.15 Å)