While misfolded and short-lived proteins are degraded in proteasomes located in the rnnucleus and cytoplasm, the degradation of organelles and long-lived proteins in the rnlysosome occurs by the process of autophagy. Central and necessary to the autophagic process are two conserved ubiquitin-like...

Endocytosis is an essential process undertaken by most eukaryotic cells. At its most general, the term refers to the uptake of material from the cell milieu. Cell biologists, however, have come to recognize a number of distinct modes of endocytic transport that are accompanied by differences in...

The eukaryotic cell is defined by a complex set of sub-cellular compartments that include endomembrane systems making up the exocytic and endocytic trafficking pathways. Current evidence suggests that both the function and communication between these compartments are regulated by distinct...

In this brief account we specifically address the question of how the plasma membrane-associated basal body/axoneme of the unicellular ancestor of eukaryotes has evolved into the centrosome organelle through the several attempts to multicellularity. We propose that the connection between the...

The Precambrian era records the evolution of the domain Eucarya. Although the taxonomy of fossils is often impossible to resolve beyond the level of domain, their morphology and chemistry indicate the evolution of major biological innovations. The late Archean record for eukaryotes is limited to...

More than 15 years ago, on the basis of phylogenetic analyses of a handful of anciently duplicated genes and of rRNA, Carl Woese proposed both a eubacterial rooting of the Tree of Life and a stepwise evolution of the eukaryotic cell. An important part of Woese’s paradigm was the assumption that...

All cells can be assigned to one of two categories based on the complexity of cellular rnorganization, eukaryotes and prokaryotes. Eukaryotes possess, among other distinguishing features, an intracellular dynamic membrane system through which there is a constant flow of membranes scaffolded by an...

All living organisms possess the ability to translocate proteins across biological membranes. This is a fundamental necessity since proteins function in different locations yet are rnsynthesized in one compartment only, the cytosol. Even though different transport systems exist, the pathway that...

By analyzing the morpho-physiological features of the Golgi complex, its relationship with the endoplasmic reticulum in different species, and the molecular machineries involved in intracellular transport, we conclude that; (1) all eukaryotic cells have either Golgi complexes or remnants thereof;...

The presence of a complex cytoskeletal system is a hallmark feature of eukaryotic cells, distinguishing them from their prokaryotic (bacterial or archaeal) “cousins”. No extant prokaryote studied so far possesses obvious homologues of major cytoskeletal proteins shared universally among...

Eukaryotic cilia and flagella are motile organelles built on a scaffold of doublet rnmicrotubules and powered by dynein ATPase motors. Some thirty years ago, two rncompeting views were presented to explain how the complex machinery of these motile organelles had evolved. Overwhelming evidence now...