Electron microscopy of 26 S complex containing 20 S proteasome

Abstract

A high molecular weight protease complex (26 S complex) involved in the intracellular protein degradation of ubiquitinated proteins was purified from rat liver and studied by electron microscopy. The most prevalent molecular species with best preserved symmetrical morphology had two large rectangular terminal structures attached to a thinner central one having four protein layers. We concluded that they were the closest representation of the 26 S complex so far reported. The central structure was identified as 20 S proteasome and the terminal one as recognition units for ubiquitinated proteins.

High-Contrast Observation of Unstained Proteins and Viruses by Scanning Electron Microscopy

“…The deconvolution image shows high contrast and a sharper structure (Figure 4B and Figure S2B). A pseudo-colour map and a 3D colour map (Figures 4C and 4D) show the 20S proteasome structure of length 52 nm with two visible 19S ends, which is essentially consistent with other reports [27], [28].…”

“…Doing so improved spatial resolution to 5 nm (Figure 2F). The deconvolution images of unstained IgM and 26S proteasome (Figures 3 and 4) show structural details that are consistent with previous reports [23], [27], [28]. However, for analysis of protein function, spatial resolution must be <2 nm.…”

“…The 26S proteasome contains a barrel-shaped 20S core capped on both ends by 19S particles. The overall structure is dumbbell-shaped of length 45–50 nm and a molecular mass of approximately 2.0 MDa [24]–[27]. At 120,000× magnification, we observed 26S proteasome molecules mounted onto the underside of a metal-coated SiN film irradiated with a 3.6-kV acceleration EB.…”

Cross Talk of Proteostasis and Mitostasis in Cellular Homeodynamics, Ageing, and Disease

“…The 20S CP in eukaryotes consists of 28 α -type and β -type subunits organized in four rings [ 104 ]; it carries the catalytic center with the three peptidase activities, namely, the caspase-like, trypsin-like, and chymotrypsin-like peptidase activities [ 105 , 106 ]. The 19S RP consists of 20 conserved subunits that form the two subcomplexes, known as the base and the lid [ 102 , 107 – 109 ]. The lid is composed of nine non-ATPase subunits (Rpn3, Rpns5–9, Rpn11, Rpn12, and Rpn15), while the base is composed of six AAA-type ATPases (Rpt1–6) and three non-ATPases, namely, the Rpn1, Rpn2, and Rpn13 subunits [ 108 , 110 – 113 ].…”

The proteasome under the microscope: the regulatory particle in focus

“…Low-resolution electron microscopy (EM) provided the first glimpses of the RP's three-dimensional organization, offering key insights into the architecture of the RP and its relationship to the CP 8–11 . In 1998 it was shown that the RP itself could be further dissociated into two subcomponents, and EM analysis was used to ascribe these subcomponents to two large stacked densities capping the CP, naming the proximal mass the “base”, and the distal mass the “lid” 12 .…”