Intrinsic disorder in the regulatory N-terminal domain of diacylglycerol acyltransferase 1 from Brassica napus

Proteins with multifunctional regulatory domains often demonstrate structural plasticity or protein disorder, allowing the binding of multiple regulatory factors and post-translational modifications. While the importance of protein disorder is clear, it also poses a challenge for in vitro characterization. Here, we report protein intrinsic disorder in a plant molecular system, which despite its prevalence is less studied. We present a detailed biophysical characterization of the entire cytoplasmic N-terminal domain of Brassica napus diacylglycerol acyltransferase, (DGAT1), which includes an inhibitory module and allosteric binding sites. Our results demonstrate that the monomeric N-terminal domain can be stabilized for biophysical characterization and is largely intrinsically disordered in solution. This domain interacts with allosteric modulators of DGAT1, CoA and oleoyl-CoA, at micromolar concentrations. While solution scattering studies indicate conformational heterogeneity in the N-terminal domain of DGAT1, there is a small gain of secondary structure induced by ligand binding.