Of the two Aspergillus early endosomal Rab5 paralogues, RabB recruits, in its GTP conformation, Vps19, Vps45, and Vps34, and the CORVET complex and couples acquisition of PI(3)P degradative identity with the long-distance movement of early endosomes. RabA also recruits CORVET, albeit less efficiently. The simultaneous loss of RabA and RabB is lethal.

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A potent hemolytic polypeptide, sticholysin II, has been purified to homogeneity from the sea anemone Stichodactyla helianthus. The protein produces leakage of aqueous contents of model lipid vesicles composed of either phosphatidylcholine or sphingomyelin if cholesterol is present in these membranes. The leakage has been analyzed by measuring the dequenching of the fluorescent dye 8-aminonaphthalene-1,3,6-trisulfonic acid, coencapsulated with its quencher N,N′-p-xylenebispyridinium bromide, upon dilution of the vesicle contents into the external medium. The protein displays a maximum effect on vesicles containing 20Ϫ25% cholesterol. Leakage is also produced in vesicles composed of mixtures of phosphatidylcholine and sphingomyelin, the maximum effect being observed for 20Ϫ30% sphingomyelin molar content. The extent of the leakage is dependent on the molecular mass of the vesicle entrapped solutes in the range 445Ϫ960 Da. This suggests the involvement of a pore of about 1 nm in diameter based on the limiting size observed for the leakage of the different solutes. Oligomerization of the protein is apparently involved in the membrane permeabilization, based on the kinetic analysis of the leakage process which is shown to proceed through an all-or-none mechanism.Keywords : cytolysin; lipid vesicle; membrane permeabilization; protein-lipid interaction.Stichodactyla helianthus is a sea anemone occurring in the further isolated and resolved into two cytolytic proteins, sticholysin I and II, by ion-exchange chromatography (Díaz et al., coastal waters of the Caribbean region. Like other coelenterates, it produces many toxic peptides and proteins located within in-1992; Tejuca et al., 1996), that display very different primary structure. In contrast, it has been reported that two distinct anemtracellular specialized organelles called nematocysts and employed on the tentacles for defense and/or attack. These organ-one species produce a cytolytic protein of practically identical amino acid sequence. This is the case described for equinatoxin elles sting the prey by means of a rapid projection of a hollow tubule through which the toxic polypeptides are injected. The II from Actinia equina (Belmonte et al., 1994) and tenebrosin-C (Simpson et al., 1990) from Actinia tenebrosa. toxicity of these products, many of them are lethal substances, has been known for a long time. They can be divided into lowCytolysin III from S. helianthus, the most studied sea anemone toxin, was described as a potent hemolytic factor (Bernmolecular-mass (3Ϫ5 kDa) neurotoxins affecting sodium channels, and single polypeptide chain proteins (15Ϫ20 kDa), cyto-heimer and Avigad, 1976), although the extent of the effect was different depending on the origin of the mammalian erythrocytes lysins, acting on cell membranes (cytolytic effects towards red blood cells, platelets and fibroblasts have been reported ; Kem, considered. It was further demonstrated that the toxin increases the membrane permeability to small ions and solutes, probably 1988; Bernheimer...

The oligomeric complex transport protein particle I (TRAPPI) mediates nucleotide exchange on the RAB GTPase RAB1/Ypt1. TRAPPII is composed of TRAPPI plus three additional subunits, Trs120, Trs130, and Trs65. Unclear is whether TRAPPII mediates nucleotide exchange on RAB1/Ypt1, RAB11/Ypt31, or both. In Aspergillus nidulans, RabO RAB1 resides in the Golgi, RabE RAB11 localizes to exocytic post-Golgi carriers undergoing transport to the apex, and hypA encodes Trs120.

Highly motile fungal early endosomes can be easily distinguished from more static late endosomes and vacuoles, a feature that is exploited to study endosomal maturation. RabA/RabB early endosomes mature into RabSRab7 late endosomes as they move away from the tip where endocytosis predominates, augmenting their size, with concomitant loss of motility.