Oligomeric assemblies of plant biotin carboxylase: structural coordinates of a cross-linked dimer of dimers

Due to the interest in fatty acid synthesis by oilseed crops, we conducted structural studies of the biotin carboxylase (BC) subunit of the plastid acetyl-CoA carboxylase from pennycress. The starting structural model of this study was the dimer of this plant BC, determined by cryo-EM by Madison et al. (2026, DOI 10.1042/BCJ20250372) and deposited under PDB 9ZVM. We formed cross-links between dimers of pennycress BC using a cross-linker cleavable in the mass spectrometer (DSBU). Cross-links guided HADDOCK docking calculations suggesting a dimer of dimers of pennycress BC that is asymmetric, staggered, and tilted between dimers, with conservation in the interface (Madison et al., 2026, DOI 10.1042/BCJ20250372). These dimer interactions conceivably may contribute to larger oligomers of BC and influence associations with other subunits of the heteromeric acetyl-CoA carboxylase from plants.