5VKO:
reference: A novel SH2 recognition mechanism recruits Spt6 to the doubly phosphorylated RNA polymerase II linker at sites of transcription., Sdano MA, Fulcher JM, Palani S, Chandrasekharan MB, Parnell TJ, Whitby FG, Formosa T, Hill CP, Elife. 2017 Aug 16;6. pii: e28723. doi: 10.7554/eLife.28723. PMID: 28826505

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).