How ractopamine binds to bovine serum albumin at the drug site 1

Abstract

ABSTRACT Ractopamine (RAC) is a common -agonist often used as a feed additive to improve muscle mass in farm animals. However, RAC has been banned in several countries due to its toxicity. To date, no clear evidence shows pharmacological and poisonous adverse effect of RAC in farm animals. In beef cattle, although RAC can be carried by bovine serum albumin (BSA) at drug site I, its effect on BSA structure and function remains unclear. Thus, in this work, Molecular Dynamics (MD) Simulations were employed to explore the binding interactions of RAC to BSA. Seemingly, RAC causes the high flexibility of domains I and III and importantly induces the large expansion of drug site II’s cavity which can interfere the drug-binding ability of drug site II. RAC binds to drug site I close to subdomain IIA, which is the same naproxen-binding site. Like naproxen, a polar moiety of RAC interacts with R194, R198 and W213. Our results reveal the RAC intrusion into the fatty acid site 6 (FA6) which implies the connection between drug site I and FA6 site. An insight into the RAC-BSA binding here can act as a base to better understand a drug distribution and bioavailability in cattle.