Architecture of the spinach plastid-encoded RNA polymerase

The plastid-encoded RNA polymerase (PEP) serves as the principal transcription machinery within chloroplasts and is responsible for transcribing over 80% of primary plastid transcripts. Plant PEP is composed of a prokaryotic-like multisubunit core enzyme known as the PEP core, supplemented by newly evolved PEP-associated proteins (PAPs). In this study, we present the cryo-electron microscopy (cryo-EM) structure of a PEP complex derived from spinach (Spinacia oleracea). Our structural analysis unveils the presence of 14 PAPs closely associated with the PEP core complex consisting of 5 subunits, forming an irregular-shaped supercomplex. We provide a detailed depiction of the PEP core subunits and the 14 PAPs, elucidating their precise spatial arrangement and interactions. This research offers a crucial structural basis for future investigations into the functions and regulatory mechanisms governing plastid transcription.