Structure of Hordeum vulgare NADPH-dependent thioredoxin reductase 2. Unwinding the reaction mechanism

Thioredoxins (Trxs) are protein disulfide reductases that regulate the intracellular redox environment and are important for seed germination in plants. Trxs are in turn regulated by NADPH-dependent thioredoxin reductases (NTRs), which provide reducing equivalents to Trx using NADPH to recycle Trxs to the active form. Here, the first crystal structure of a cereal NTR, HvNTR2 from Hordeum vulgare (barley), is presented, which is also the first structure of a monocot plant NTR. The structure was determined at 2.6 Å resolution and refined to an R (cryst) of 19.0% and an R (free) of 23.8%. The dimeric protein is structurally similar to the structures of AtNTR-B from Arabidopsis thaliana and other known low-molecular-weight NTRs. However, the relative position of the two NTR cofactor-binding domains, the FAD and the NADPH domains, is not the same. The NADPH domain is rotated by 25° and bent by a 38% closure relative to the FAD domain in comparison with AtNTR-B. The structure may represent an intermediate between the two conformations described pre­viously: the flavin-oxidizing (FO) and the flavin-reducing (FR) conformations. Here, analysis of interdomain contacts as well as phylogenetic studies lead to the proposal of a new reaction scheme in which NTR–Trx interactions mediate the FO to FR transformation

User Needs Assessment of Information Seeking Activities of MIT Students - Spring 2006

The SFX/Verde Group was authorized to complete a user needs assessment in the form of a Photo Diary Study with MIT students in the spring of 2006. The goal of the study was to inform the MIT Libraries of online tool improvements that should be implemented to meet our most pressing user needs. Sixteen graduate students and sixteen undergraduate students participated in offering a fascinating glimpse into the information-seeking aspects of their academic lives. The team categorized user behaviors into goals and tasks and then analyzed the 277 goals and tasks and the 507 methods shared with us by the students in the study. The study yielded the following priorities for the Libraries' online tools: Make discovery easier and more effective. Incorporate trusted networks in finding tools. Continue to put links to the Libraries' services and resources where the users are. The study also showed that the students used a variety of highly successful strategies for performing quick lookups of information and finding specific known items. Finally, while the assessment focused on aspects of the students' work related to online tools, it also yielded rich information that could be useful in improving other aspects of the Libraries' services