Biliverdin reductase B (BLVRB) is a newly identified cellular redox regulator that catalyzes the NADPH-dependent reduction of multiple substrates. Through mass spectrometry analysis, we identified high levels of BLVRB in mature red blood cells, highlighting the importance of BLVRB in redox regulation. The BLVRB conformational changes that occur during conezyme/substrate binding and the role of dynamics in BLVRB function, however, remain unknown. Through a combination of NMR, kinetics, and isothermal titration calorimetry studies, we determined that BLVRB binds its coenzyme 500-fold more tightly than its substrate. While the active site of apo BLVRB is highly dynamic on multiple timescales, active site dynamics are largely quenched within holo BLVRB, in which dynamics are redistributed to other regions of the enzyme. We show that a single point mutation of Arg78➔Ala leads to both an increase in active site micro-millisecond motions and an increase in the microscopic rate constants of coenzyme binding. This demonstrates that altering BLVRB active site dynamics can directly cause a change in functional characteristics. Our studies thus address the solution behavior of apo and holo BLVRB and identify a role of enzyme dynamics in coenzyme binding.

No abstract

This workshop began an important collaborative effort to assess the threat of waterborne cryptosporidiosis to public health. Representatives from 40 states and from regulatory and public health agencies, water utilities, and advocacy groups met last year to discuss prevention and control of waterborne cryptosporidiosis. Workgroups addressed surveillance systems and epidemiologic study designs, public health responses when oocysts are detected in drinking water, cryptosporidiosis in immunocompromised individuals, and water sampling methods and interpretation of results. The groups defined problems associated with these issues and developed strategies that could be used initially to manage these problems. An outgrowth of the workshop has been the formation of the Working Group on Waterborne Cryptosporidiosis, which holds regular teleconferences. In addition, several task forces are working to address strategies proposed in this report.