Development of an optimized feeding technology for dairy cows

We have previously reported on MB-1, a designer protein with potential appl ication in animal nutrition. Having a high content of selected essential am ino acids, MB-1 should provide limiting nutrients for animals and promote g rowth and production. However, the protein was found to have marginal confo rmational and proteolytic stability, and, thus, strategies for stabilizing MB-1 were elaborated. We discuss the synthesis of MB-1-Cys dimer, a protein with an intermolecular disulfide bridge. This mutant was exposed to Pronas e E protease preparation as well as to proteases extracted from ruminal mic robes. It was found that in both cases, MB-1-Cys dimer had a better resista nce to proteolytic degradation than MB-1. Denaturation and hydrophobic dye binding studies revealed that this enhanced stability was not owing to conf ormational stabilization, but rather to changes in surface exposure as a co nsequence of dimerization. In particular, it was found that binding of ANSA to MB-1-Cys dimer was comparable to that observed for native, compact, nat ural proteins. We discuss the implications of these results for the design of transgenic protein production systems.