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The crystal structure of the ttCsaA protein: an export‐related chaperone from Thermus thermophilus
Author(s) -
Kawaguchi Shinichi,
Müller Jörg,
Linde Dirk,
Kuramitsu Seiki,
Shibata Takehiko,
Inoue Yorinao,
Vassylyev Dmitry G.,
Yokoyama Shigeyuki
Publication year - 2001
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/20.3.562
Subject(s) - thermus thermophilus , library science , national laboratory , biology , physics , genetics , gene , engineering physics , computer science , escherichia coli
The CsaA protein was first characterized in Bacillus subtilis as a molecular chaperone with export‐related activities. Here we report the 2.0 Å‐resolution crystal structure of the Thermus thermophilus CsaA protein, designated ttCsaA. Atomic structure and experiments in solution revealed a homodimer as the functional unit. The structure of the ttCsaA monomer is reminiscent of the well known oligonucleotide‐binding fold, with the addition of extensions at the N‐ and C‐termini that form an extensive dimer interface. The two identical, large, hydrophobic cavities on the protein surface are likely to constitute the substrate binding sites. The CsaA proteins share essential sequence similarity with the tRNA‐binding protein Trbp111. Structure‐based sequence analysis suggests a close structural resemblance between these proteins, which may extend to the architecture of the binding sites at the atomic level. These results raise the intriguing possibility that CsaA proteins possess a second, tRNA‐binding activity in addition to their export‐related function.