12 Results
for term "sites"
- Mitochondrial Protein Synthesis, Import, and Assembly...tubular structures at sites termed crista junctions and expand as they project into the matrix (Frey and Mannella 2000; Mannella et al. 2001) (Figure 1B). It seems clear that the boundary and cristae domains of the inner membrane have distinct compositions with respect to the respiratory complexes ~~~
- Secretory Protein Biogenesis and Traffic in the Early Secretory Pathway...? These questions were addressed in part by the Glick and Nakano labs using highresolution time-lapse imaging of living yeast cells (Losev et al. 2006; Matsuura-Tokita et al. 2006). Such experiments dened discrete sites of vesicle formation, known as transitional ER (tER) or ER exit sites (ERES), that are dynamic ~~~
- The Ubiquitin–Proteasome System of Saccharomyces cerevisiae...: Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, EN6 3LD, United Kingdom. E-mail: Helle.Ulrich@ cancer.org.uk Genetics, Vol. 192, 319360 October 2012 319 CONTENTS, continued Initiation sites: 334 Rpt ring: 334 Interface between the RP and CP: 334 Blm10 ~~~
- The Yeast Nuclear Pore Complex and Transport Through It...eukaryotes with a critical control mechanism segregating the sites of gene transcription and ribosome biogenesis from the site of protein synthesis. This compartmentalization allows cells to strictly coordinate numerous key cellular processes, but it also presents cells with the challenge of selectively ~~~
- Mitotic Spindle Form and Function...to the inner (nuclear side) and outer (cytoplasmic side) plaques, respectively, by strut proteins that span the gap between these layers of the SPB. The inner and outer plaques are critically important because they are the sites from which microtubules are nucleated. The sole strut protein connecting ~~~
- Lipid Droplets and Peroxisomes: Key Players in Cellular Lipid Homeostasis or A Matter of Fat—Store ’em Up or Burn ’em Down...Peroxisome Biogenesis 30 Peroxisomal matrix protein import 30 Targeting signals and their receptors: 30 PTS1 and its receptor Pex5: 30 PTS2 and Pex7 with its coreceptors: 31 Piggy-back import: 31 Receptor docking site: 31 RING nger complex: 32 Translocation pore: 33 Receptor recycling and the role ~~~
Figure 10Balance of dynamic pushing and pulling forces in S. cerevisiae.To properly position the pre-anaphase spindle at the bud neck without moving the spindle into the bud, S. cerevisiae provides a balance of pushing and pulling forces (arrows). (A) Growing and shortening microtubules in the mother cell facilitate searching of the cytoplasmic space and establish pushing forces against the cortex to orient the spindle to the bud neck. (B) Stable attachment at the neck could provide a stabilizing force to limit pulling forces from the bud; it could also provide a loading site for actin-based transport of microtubules and dynein-dependent sliding, and/or it could maintain proper positioning at the bud neck. (C) Minus-end-directed movement of cortically anchored dynein provides a strong pulling force to bring the spindle to the bud neck. Dynein is off-loaded to cortical anchors (Num1) where the minus-end activity is stimulated to result in a pulling force that brings the nucleus into the bud (Lee et al. 2005; Markus and Lee 2011). (D) In a redundant pathway, microtubule plus ends are linked through Bim1 and Kar9 to class-V myosin (Myo2) that is moving along polarized actin arrays, facilitating plus-end transport to the bud site. In addition, transport might generate pulling forces to pull the spindle to the bud neck. (E) Finally, end-on attachment at the bud tip where formin nucleates actin growth may also generate force by maintaining attachment to both growing and shortening microtubule plus ends. Adapted from Pearson and Bloom (2004).
Figure 1Protein ubiquitylation. (A) Ubiquitin is activated by E1 in an ATP-dependent step, transferred to the active site cysteine in an ubiquitin-conjugating enzyme (E2), and covalently attached to substrate proteins. Substrate selection depends on ubiquitin ligases (E3). Conjugation of a single ubiquitin molecule generates monoubiquitylated proteins. Repeated rounds of ubiquitin activation and conjugation lead to multi- or polyubiquitylated proteins. (B) Different polyubiquitin chain topologies can be synthesized depending on the specific lysine residue in ubiquitin used for chain formation. Three of the eight possible unbranched chain topologies (K6, K11, K27, K29, K33, K48, K63, and linear chains), and only one type of the possible forked polyubiquitin chains are shown. (C) Structural model for synthesis of K63-linked polyubiquitin chains by Ubc13/Mms2. Mms2 positions the acceptor ubiquitin with K63 in proximity to the active site cysteine of Ubc13. Figure adapted with permission from Macmillan Publishers Ltd: Chan, N. L., and C. P. Hill, 2001 Nat. Struct. Biol. 8: 650–652.
Figure 4Proteasome core particle. (A) Space-filling exterior view of the CP, with subunits differentiated by color. Note the α7β7β7α7 organization. (B) Medial cut-away view of the CP, showing the interior cavity and active sites (red) sequestered within it. The substrate transloction channel is fully closed in the crystal structure of the free CP, but brackets indicate the approximate position of the channel in its open state. (C) Detail of the CP gate. The N-terminal tails of the α subunits, particularly α2, α3, and α4, as shown, block substrate access. The bodies of the α subunits are rendered in gray. Arrow indicates the movement of the tails that constitutes gate opening, a likely upward and outward migration (Förster et al. 2003). Images modified from Groll et al. 1997 and Tian et al. 2011, with permission.
Figure 5The proteasome holoenzyme. (A) Model of the Rpt ring of the proteasome in association with the yeast CP. Medial cut-away view, with the Rpt ring modeled from observations of the PAN ATPase from Archaea (adapted from Zhang et al. 2009b, with permission). The ATPase domain of the Rpt ring and the smaller OB domain above it both in blue. Coiled-coil elements (turquoise) emerge distally from the OB domain with their trajectory influenced by Pro91 (pink). The CP is in green, with proteolytic sites in red. Slice surfaces of the CP and Rpt ring are in black. The presumptive substrate translocation channel is demarcated with yellow lines: The entry port of the translocation channel is thought to be the OB ring, and substrates must migrate to the proteolytic active sites (red) to be hydrolyzed. The driving force for translocation is thought to be axial motions of the pore loops from the ATPase domain that line the translocation channel (gold rectangles). (B) Tilted view of the RP based on EM studies (Lander et al. 2012). The Rpt ring and CP are colored as in A. The DUB Rpn11 is in turquoise, with the presumptive substrate entry port directly beneath it (red-orange). The ubiquitin receptor Rpn13 is in orange. To its left is Ubp6 (approximate position), contacting Rpn1. To the right is Rpn10, with its Von Willebrand A (VWA) domain in yellow and its ubiquitin-binding UIM domain in red. All other RP subunits are in gray. Shown for comparison at upper right is free ubiquitin (pink). (C) Lateral view of the RP (derived from Lander et al. 2012). Highlighted are Rpn1 (red-orange), Rpn2 (pink), Rpn13 (orange), and Rpn10 (yellow). Lid subunits are in gray. B and C are from Tian et al. (2012), with permission.