6xpj
CutR flat hexamer, form 2
Structural highlights
FunctionCUTR_STRIS A minor shell protein of the choline degradation-specific bacterial microcompartment (BMC). Proteins such as this one with circularly permuted BMC domains may play a key role in conferring heterogeneity and flexibility in this BMC.[1] Publication Abstract from PubMedBacterial microcompartments are protein-based organelles that carry out specialized metabolic functions in diverse bacteria. Their outer shells are built from several thousand protein subunits. Some of the architectural principles of bacterial microcompartments have been articulated, with lateral packing of flat hexameric BMC proteins providing the basic foundation for assembly. Nonetheless, a complete understanding has been elusive, partly owing to polymorphic mechanisms of assembly exhibited by most microcompartment types. An earlier study of one homologous BMC shell protein subfamily, EutS/PduU, revealed a profoundly bent, rather than flat, hexameric structure. The possibility of a specialized architectural role was hypothesized, but artifactual effects of crystallization could not be ruled out. Here we report a series of crystal structures of an orthologous protein, CutR, from a glycyl-radical type choline-utilizing microcompartment from the bacterium Streptococcus intermedius. Depending on crystal form, expression construct, and minor mutations, a range of novel quaternary architectures was observed, including two spiral hexagonal assemblies. A new graphical approach helps illuminate the variations in BMC hexameric structure, with results substantiating the idea that the EutS/PduU/CutR subfamily of BMC proteins may endow microcompartment shells with flexible modes of assembly. Symmetry breaking and structural polymorphism in a bacterial microcompartment shell protein for choline utilization.,Ochoa JM, Nguyen VN, Nie M, Sawaya MR, Bobik TA, Yeates TO Protein Sci. 2020 Sep 4. doi: 10.1002/pro.3941. PMID:32885887[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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