Cell Biology

... from active transport to vesicles


Lysosomes are generated by the Golgi apparatus of animal and plant cells and contain digestive enzymes, which include carbohydrases, lipases, nucleases, and proteases. The enzymes are produced in the endoplasmic reticulum and processed by the Golgi apparatus, from which the lysosomes bud as vesicles.

Degradation of Ubiquitin-conjugated proteins is performed by the intracellular protease known as the 26S proteasome. The ubiquitin-proteasome proteind degradation pathway is also termed endoplasmic reticulum associated degradation (ERAD). After ERAD substrates are selected in the ER, they are exported, or "retro-translocated" to the cytoplasm and destroyed by the cytoplasmic proteasome, a large multi-catalytic protease with a central barrel where unfolded Ub-tagged proteins are hydrolyzed. Reported in a paper in EMBO J., are findings that the proteasome itself can provide the driving force for translocation. The cap, or 19S particle can hydrolyze ATP and extract a polypeptide from the ER.[s]

Џ beautiful Flash 8 animation - Inner Life of the Cell, which shows vesicles budding from the Golgi complex ; and, Interpretation: Inner Life of the Cell Џ

[] 26s proteasome [] 3D structure of targetted peptide [] barrel and subunits of proteasome [] proteasome assembly [] proteasome engine [] substrate swapping [] Ub-proteasome pathway [] yeast 20s proteasome ribbon, yeast 20s proteasome down the barrel, surface with bound aldehyde indicators Џ animation - proteasome Џ animation - importing, unfolding, hydrolyzing Џ

Aberrant Ub-mediated protein degradation has been implicated in a number of pathological conditions, particularly neurodegenerative disorders that involve protein aggregation and inclusion body formation, where protein misfolding may play a role –Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and ALS.

: diag. ubiquitin-mediated degradation :

• A • adhesion • C • cell membranescellular adhesion moleculescellular signal transductioncentrioleschemotaxischloroplastcilia & flagellacommunicationconcentration gradientscytokine receptorscytoplasmcytoskeleton • E • energy transducersendoplasmic reticulumendosomesexosome • F • flagella & cilia • G • Golgi apparatusGPCRs • H • hormones • I • ion channels • L • lysosome • M • meiosismicrotubulesmitosismitochondrion • N • Nitric Oxideneurotransmissionneuronal interconnectionsnuclear membranenuclear pore • P • pinocytosisproteasomepumps • R • receptor proteinsreceptor-mediated endocytosis • S • second messengerssignaling gradientssignal transductionspindlestructure • T • transporttwo-component systems • V • vacuolevesicle

animation - golgi apparatus and budding golgi body : animation - golgi at work : animation - lysosomes "suicide sacks" : tour lysosome : Virtual Cell Textbook - Cell Biology :

. . . developing since 10/06/06