Sequence divergent features in coronavirus nsp12.A, a multiple sequence alignment of IBV, SARS-CoV-2, and PEDV nsp12 highlights sequence and structurally divergent regions in the N-terminal region of nsp12. B, an overview of the IBV replication-transcription complex indicates the locations of structurally divergent nsp12 regions shown in greater detail in C–E. C, an insertion in IBV nsp12 67 to 72 presents as an extended loop. Reconstructed IBV RTC density is shown with superimposed PEDV (8URB) and SARS-CoV-2 (6XEZ) structures. D, IBV nsp12 has a shortened loop in the 113 to 115 region (IBV reconstructed density) as compared to SARS-CoV-2 and PEDV nsp12. E, an insertion in IBV nsp12 156 to 169 (IBV reconstructed density) presents as an altered conformation compared to SARS-CoV-2 and PEDV. IBV, infectious bronchitis virus; nsp, nonstructural protein; PEDV, porcine epidemic diarrhea virus; RTC, replication–transcription complex.