The effect of a continuous supply of betaine on the degradation of betaine in the rumen of dairy cows.

We investigated the degradation of betaine in the rumen by a continuous supply of betaine to dairy cows. After 24 h of betaine incubation using rumen fluid from dairy cows, more than 80% of the betaine remained undegraded. Furthermore, the continuous supply of betaine for about 70 d did not influence the in vitro degradation of betaine.

Structural basis for the assembly of the Ragulator-Rag GTPase complex.

The mechanistic target of rapamycin complex 1 (mTORC1) plays a central role in regulating cell growth and metabolism by responding to cellular nutrient conditions. The activity of mTORC1 is controlled by Rag GTPases, which are anchored to lysosomes via Ragulator, a pentameric protein complex consisting of membrane-anchored p18/LAMTOR1 and two roadblock heterodimers. Here we report the crystal structure of Ragulator in complex with the roadblock domains of RagA-C, which helps to elucidate the molecular basis for the regulation of Rag GTPases. In the structure, p18 wraps around the three pairs of roadblock heterodimers to tandemly assemble them onto lysosomes. Cellular and in vitro analyses further demonstrate that p18 is required for Ragulator-Rag GTPase assembly and amino acid-dependent activation of mTORC1. These results establish p18 as a critical organizing scaffold for the Ragulator-Rag GTPase complex, which may provide a platform for nutrient sensing on lysosomes.