6VWP:
reference: ppGpp Coordinates Nucleotide and Amino-Acid Synthesis in E. coli During Starvation., Wang B, Grant RA, Laub MT, Mol Cell. 2020 Oct 1;80(1):29-42.e10. doi: 10.1016/j.molcel.2020.08.005. Epub, 2020 Aug 27. PMID: 32857952

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