3j9i
From Proteopedia
Thermoplasma acidophilum 20S proteasome
Structural highlights
Function[PSA_THEAC] Component of the proteasome core, a large protease complex with broad specificity involved in protein degradation. The T.acidophilum proteasome is able to cleave oligopeptides after Tyr, Leu, Phe, and to a lesser extent after Glu and Arg. Thus, displays chymotrypsin-like activity and low level of caspase-like and trypsin-like activities.[1] [PSB_THEAC] Component of the proteasome core, a large protease complex with broad specificity involved in protein degradation. The T.acidophilum proteasome is able to cleave oligopeptides after Tyr, Leu, Phe, and to a lesser extent after Glu and Arg. Thus, displays chymotrypsin-like activity and low level of caspase-like and trypsin-like activities.[2] Publication Abstract from PubMedIn recent work with large high-symmetry viruses, single-particle electron cryomicroscopy (cryo-EM) has achieved the determination of near-atomic-resolution structures by allowing direct fitting of atomic models into experimental density maps. However, achieving this goal with smaller particles of lower symmetry remains challenging. Using a newly developed single electron-counting detector, we confirmed that electron beam-induced motion substantially degrades resolution, and we showed that the combination of rapid readout and nearly noiseless electron counting allow image blurring to be corrected to subpixel accuracy, restoring intrinsic image information to high resolution (Thon rings visible to approximately 3 A). Using this approach, we determined a 3.3-A-resolution structure of an approximately 700-kDa protein with D7 symmetry, the Thermoplasma acidophilum 20S proteasome, showing clear side-chain density. Our method greatly enhances image quality and data acquisition efficiency-key bottlenecks in applying near-atomic-resolution cryo-EM to a broad range of protein samples. Electron counting and beam-induced motion correction enable near-atomic-resolution single-particle cryo-EM.,Li X, Mooney P, Zheng S, Booth CR, Braunfeld MB, Gubbens S, Agard DA, Cheng Y Nat Methods. 2013 Jun;10(6):584-90. doi: 10.1038/nmeth.2472. Epub 2013 May 5. PMID:23644547[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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