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High-resolution cryo-EM structure of Maltose Binding Protein
Structural highlights
FunctionMALE_ECOLI Involved in the high-affinity maltose membrane transport system MalEFGK. Initial receptor for the active transport of and chemotaxis toward maltooligosaccharides. Publication Abstract from PubMedCryo-electron microscopy (cryo-EM) is a widely used technique for determining macromolecular structures at near-atomic resolution. The theoretical lower limit of particle sizes suitable for cryo-EM structural analysis is estimated to be 38 kDa; typical constraints involve factors such as image contrast and particle alignment accuracy. In this study, we present cryo-EM structures of two protein-ligand complexes near this lower size threshold. First, the structure of the maltose-binding protein complexed with maltose, with a structurally ordered mass of 40.8 kDa, was determined at a resolution of 2.4 A; both the maltose and water molecules were clearly identified in this structure. The second structure was the kinase domain of human PLK1 complexed with onvansertib, with a structurally ordered mass of 31.6 kDa, below the theoretical 38 kDa limit; this domain was determined at a resolution of 3.4 A using a gold-supported grid in the presence of beta-octyl-glucoside. The density map clearly shows the backbone of PLK1 secondary structure, and the onvansertib. These results demonstrate that cryo-EM can be effectively employed to determine structures of small proteins or domains, and to perform structure-based drug screening for small proteins, without requiring structural fiducials for particle alignment. High-resolution cryo-EM structures of small protein-ligand complexes near the theoretical size limit.,Park K, Yoo Y, Jeon H, Choi K, Kim H, Kwon E, Lim HH, Kim DY, No KT Nat Commun. 2026 Apr 14. doi: 10.1038/s41467-026-71934-7. PMID:41980966[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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