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Solution structure of the LicT–RNA antitermination complex: CAT clamping RAT
Author(s) -
Yang Yinshan,
Declerck Nathalie,
Manival Xavier,
Aymerich Stéphane,
Kochoyan Michel
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/21.8.1987
Subject(s) - physics , humanities , philosophy
LicT is a bacterial regulatory protein able to prevent the premature arrest of transcription. When activated, LicT binds to a 29 base RNA hairpin overlapping a terminator located in the 5′ mRNA leader region of the target genes. We have determined the solution structure of the LicT RNA‐binding domain (CAT) in complex with its r ibonucleic a nti t erminator (RAT) target by NMR spectroscopy (PDB 1L1C). CAT is a β‐stranded homodimer that undergoes no important conformational changes upon complex formation. It interacts, through mostly hydrophobic and stacking interactions, with the distorted minor groove of the hairpin stem that is interrupted by two asymmetric internal loops. Although different in sequence, these loops share sufficient structural analogy to be recognized similarly by symmetry‐related elements of the protein dimer, leading to a quasi‐ symmetric structure reminiscent of that observed with dimeric transcription regulators bound to palindromic DNA. Sequence analysis suggests that this RNA‐ binding mode, where the RAT strands are clamped by the CAT dimer, is conserved in homologous systems.