DNA may be the master blueprint for life, but it is of proteins that we're built. While many of them are structurally simple, there are approximately 7,000 proteins that must be made in a cell's secretory pathway and will be either dispersed throughout the cell or secreted to the extracellular space in order to perform their essential functions. Senior authors Daniel Hebert, professor of biochemistry and molecular biology at UMass Amherst, and Lila Gierasch, distinguished professor of biochemistry and molecular biology and chemistry at UMass Amherst, along with co-author, Kevin Guay, a graduate student in the molecular cellular biology program at UMass Amherst, had shown in previous research that UGGT acts as a "gatekeeper" by reading carbohydrate tags, called N-glycans, embedded into the protein to determine whether or not the protein is correctly folded.

 

Using an AI model called AlphaFold2, Williams and his co-authors predicted that the protein Sep15 forms a complex helical shape that looks something like a catcher's mitt, and that this mitt perfectly matches a complementary site on the UGGT enzyme. The specific site where SEP15 and UGGT bind is also where UGGT reads the N-glycan code that tells it whether or not a protein is correctly folded. To test their AlphaFold2-generated prediction, the research team designed an experiment using recombinant DNA re-engineering of UGGT to interrupt its binding to Sep15 -- and, indeed, the modified UGGT failed to form a complex with Sep15. "The complexity of the proteins we are studying allows higher forms of life to function," says Gierasch, "but the complexity of those proteins also means that they're more prone to misfolding errors, and misfolding errors can have catastrophic consequences if the quality control process fails."

 

Though there is still a great deal of basic research to be done, the team's research sets the stage for novel drug therapies that target the Sep15/UGGT interface. "This is an untapped pharmaceutical area," says Hebert, "and Williams's research has moved us in the right direction for eventual treatment." This research was supported by the National Institutes of General Medical Sciences and facilitated by the availability of instrumentation in the UMass Amherst Institute for Applied Life Sciences.