The repeat domain of the type III effector protein PthA shows a TPR-like structure and undergoes conformational changes upon DNA interaction

Authors

  • Mário Tyago Murakami,

    Corresponding author
    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    • Laboratório Nacional de Biociências, Centro Nacional de Energia e Materiais, R. Giuseppe Máximo Scolfaro, 10000, Campinas, SP, 13083-970, Brazil
    Search for more papers by this author
  • Mauricio Luis Sforça,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • Jorge Luiz Neves,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • Joice Helena Paiva,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • Mariane Noronha Domingues,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • André Luiz Araujo Pereira,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • Ana Carolina de Mattos Zeri,

    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    Search for more papers by this author
  • Celso Eduardo Benedetti

    Corresponding author
    1. Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970, Campinas, SP, Brazil
    • Laboratório Nacional de Biociências, Centro Nacional de Energia e Materiais, R. Giuseppe Máximo Scolfaro, 10000, Campinas, SP, 13083-970, Brazil
    Search for more papers by this author

Abstract

Many plant pathogenic bacteria rely on effector proteins to suppress defense and manipulate host cell mechanisms to cause disease. The effector protein PthA modulates the host transcriptome to promote citrus canker. PthA possesses unusual protein architecture with an internal region encompassing variable numbers of near-identical tandem repeats of 34 amino acids termed the repeat domain. This domain mediates protein–protein and protein–DNA interactions, and two polymorphic residues in each repeat unit determine DNA specificity. To gain insights into how the repeat domain promotes protein–protein and protein–DNA contacts, we have solved the structure of a peptide corresponding to 1.5 units of the PthA repeat domain by nuclear magnetic resonance (NMR) and carried out small-angle X-ray scattering (SAXS) and spectroscopic studies on the entire 15.5-repeat domain of PthA2 (RD2). Consistent with secondary structure predictions and circular dichroism data, the NMR structure of the 1.5-repeat peptide reveals three α-helices connected by two turns that fold into a tetratricopeptide repeat (TPR)-like domain. The NMR structure corroborates the theoretical TPR superhelix predicted for RD2, which is also in agreement with the elongated shape of RD2 determined by SAXS. Furthermore, RD2 undergoes conformational changes in a pH-dependent manner and upon DNA interaction, and shows sequence similarities to pentatricopeptide repeat (PPR), a nucleic acid-binding motif structurally related to TPR. The results point to a model in which the RD2 structure changes its compactness as it embraces the DNA with the polymorphic diresidues facing the interior of the superhelix oriented toward the nucleotide bases. Proteins 2010. © 2010 Wiley-Liss, Inc.

Ancillary