NATURE CHEMICAL BIOLOGY | ARTICLE
Po-ssu Huang1,2,6*, Kaspar Feldmeier3,6, Fabio Parmeggiani1,2, D Alejandro Fernandez Velasco4,
Birte Höcker3* & David Baker1,2,5*
1department of biochemistry, university of Washington, Seattle, Washington, uSA. 2institute for protein design, university of Washington, Seattle,
Washington, uSA. 3Max planck institute for developmental biology, tübingen, Germany. 4Facultad de Medicina, universidad nacional Autónoma de
México (unAM), ciudad universitaria, México dF, Mexico. 5Howard Hughes Medical institute, university of Washington, Seattle, Washington, uSA.
Despite efforts for over 25 years, de novo protein design has not succeeded in achieving the TIM-barrel fold. Here we describe
the computational design of four-fold symmetrical (b/a)8 barrels guided by geometrical and chemical principles. Experimental
characterization of 33 designs revealed the importance of side chain–backbone hydrogen bonds for defining the strand register
between repeat units. The X-ray crystal structure of a designed thermostable 184-residue protein is nearly identical to that of
the designed TIM-barrel model. PSI-BLAST searches do not identify sequence similarities to known TIM-barrel proteins, and
sensitive profile-profile searches indicate that the design sequence is distant from other naturally occurring TIM-barrel super-
families, suggesting that Nature has sampled only a subset of the sequence space available to the TIM-barrel fold. The ability
to design TIM barrels de novo opens new possibilities for custom-made enzymes.
ワシントン大のDavid Baker先生らのお仕事です。βシート構造を含むタンパク質のDe novo設計が未だ困難な状況で、天然のものとはまったく異なるTIMバレルを構築したという内容です。4回リピート構造に基づいたRossetRemodel計算から導かれる、最小安定エネルギーを持った33の候補(最終的には２２)を対象に実験的に検証したそうです。最も熱安定性の高かったsTIM1(Tm=72℃)の構造はモデルとほぼ一致(RMSD(Cα)=1.24Å, 184残基)しています。また、sTIM1のVariantsから安定性と軸対称性の議論も行われており、タンパク質化学者にとっては非常に興味をそそられる内容となっています。それに加えてTIMバレルは普遍的モチーフの１つであり、カスタムメイドな酵素の土台として用いられることが多く、人工酵素研究の新たな可能性を切り開くきっかけにもなると述べられています。
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