A Critical Inter-Subunit Interaction for the Transmission of the Allosteric Signal in the Agrobacterium Tumefaciens ADP-Glucose Pyrophosphorylase

ADP-glucose pyrophosphorylase is a key regulatory enzyme involved in starch and glycogen synthesis in plants and bacteria, respectively. It has been hypothesized that inter-subunit communications are important for the allosteric effect in this enzyme. However, no specific interactions have been identified as part of the regulatory signal. The enzyme from Agrobacterium tumefaciens is a homotetramer allosterically regulated by fructose 6-phosphate and pyruvate. Three pairs of distinct subunit-subunit interfaces are present. Here we focus on an interface that features two symmetrical interactions between Arg11 and Asp141 from one subunit with residues Asp141 and Arg11 of the neighbor subunit, respectively. Previously, scanning mutagenesis showed that a mutation at the Arg11 position disrupted the activation of the enzyme. Considering the distance of these residues from the allosteric and catalytic sites, we hypothesized that the interaction between Arg11 and Asp141 is critical for allosteric signaling rather than effector binding. To prove our hypothesis, we mutated those two sites (D141A, D141E, D141N, D141R, R11D, and R11K) and performed kinetic and binding analysis. Mutations that altered the charge affected the regulation the most. To prove that the interaction per se (rather than the presence of specific residues) is critical, we partially rescued the R11D protein by introducing a second mutation (R11D/D141R). This could not restore the activator effect on kcat, but it did rescue the effect on substrate affinity. Our results indicate the critical functional role of Arg11 and Asp141 to relay the allosteric signal in this subunit interface

High Volume, High Acuity, and High Impact Learning: Tips and Tricks for Infectious Diseases Training Programs

Abstract The IDSA Training Program Directors Committee met in October 2022 and discussed an observed increase in clinical volume and acuity on infectious diseases (ID) services, and its impact on fellow education. Committee members sought to develop specific goals and strategies related to improving training program culture, preserving quality education on inpatient consult services and in the clinic, and negotiating change at the annual IDWeek Training Program Director meeting. This paper outlines a presentation of ideas brought forth at the meeting and is meant to serve as a reference document for ID training program directors seeking guidance in this area