= Averell L. Gnatt
{c}
<Averell L. Gnatt> studied the <protein structure> of <RNA polymerase II>, the <enzyme> that carries out much of <eukaryotic> <transcription>. In 2001, he and colleagues determined an <X-ray crystallography> structure of an actively transcribing complex at a spatial detail of $3.3\,\text{Å}$. The complex contained both the <DNA> template and the growing <RNA>, allowing their paths through the <enzyme> to be followed.<Structural Basis of Transcription: An RNA Polymerase II Elongation Complex at 3.3 Å Resolution by Averell L. Gnatt and others>[Science 292, pp. 1876–1882; abstract and elongation-complex structure]{ref}
Incoming paired <DNA> entered a cleft and separated before the <active site>. A nine-base-pair <DNA-RNA hybrid> held the newly copied region, while the growing <RNA> end lay at the site where the next <nucleotide> would be added. Thus only a short local stretch of the product remained paired to its template: the rest of the <RNA> could leave as copying continued. Comparison with the free <enzyme> also showed closure of a protein clamp over the bound <DNA> and <RNA>, connecting a change in <protein structure> with stable engagement during <transcription>.<Structural Basis of Transcription: An RNA Polymerase II Elongation Complex at 3.3 Å Resolution by Averell L. Gnatt and others>[Abstract; nine-base-pair hybrid, RNA exit groove and clamp closure]{ref}
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