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LnvEx, R., Voar, W., SCF1I~m7T, G . and DIEASIIVGER, L. (Max Planck Inst ., Exptl. Medicine,Dept . Biochem. Pharmacol West Germany) . Purification of a human serum protein (factor E)which enhances cobra venom factor-induced indirect lysis . Identification with the fifth com-

ponent of complement . Z. ImmunForsch, exp. Ther . 151, 105, 1976 .

WmTt incubated with human or other serum, cobra venom factor (CVF) interacts with the component of theproperdin system, factor B and factor D, and forms a complex which activates the late acting components ofcomplement, leading to hemolysis of red cells . The complex consists of CVF and activated factor B (B)which is a fragment of factor B(glycine-rich B glycoproteine), cleaved by factor D when factor B is bound toCVF.However, for optimal activation of the terminal complement sequence in this system of indirect lysis,

another human serum factor, called factor E, is essential. The authors have purified factor E, which is aprotein. In chromatographic fractionation it was inseparable from the fifth complement component. Theauthors concluded that factor E is the fifth component of human complement . Guinea pig CS is not capableof supporting indirect lysis in a comparable manner . Two explanations are proposed : (1) In contrast tohuman C5, guinea pig CS may not be capable of binding directly to the surface of guinea pig red cells . (2)Fixation of CS and of C567 on red cells can be impaired by inhibitors) present in guinea pig serum.

P.B .

KELLY, R. B., OHERO, S . G ., Sraoxa, P. N. and WAGNER, G. M. (Departments of Biochemistryand Physiology, University of California, San Francisco, California, U.S.A .) . ß-Bungarotoxin,a phospholipase that stimulates transmitter release. Cold Spring Harbor Symp. Quantitative

Biol . 40, 177, 1975 .

ß-BUNGAROTOXIN wmbines presynaptic neurotoxic and phospholipase AZ activities, like e.g. notexin andtaipoxin from Australian elapid venoms. The enzymatic activity seems necessary for the action at the presy-naptic terminal, since both reactions are Cat+ dependant. Srz+ ions are no substitute . On the other hand,common phospholipases are not neurotoxic, even at much higher concentrations . This difference was alsodemonstrated by comparison of inhibition of Cat+ uptake into brain mitochondria. They were much moresensitive to ß-bungarotoxin than liver mitochondria. There was no difference in sensitivity against Crotalesadamaxteus phospholipase. Further studies were focused on the early enhancement of the release of trans-mitter substance and depletion of the terminals. The authors develop a model for thedisturbance of synaptictransmission by ß-bungarotoxin summarizing all known data.

H.M.