Interaction of reduced glutathione with bovine brain tubulin

Incubation of phosphocellulose-purified tubulin with GSH at 30 degrees C results in an inhibition of colchicine binding activity. GSSG has a protective effect against the GSH-induced loss of colchicine-binding. Incubation of tubulin with GSH at 30 degrees C results in the formation of abnormal tubulin polymers which are insensitive to cold. Such aggregation is insensitive to antimicrotubular drugs. Aggregation is inhibited by GSSG but not by DTT or mercaptoethanol. GSH-induced aggregation is very sensitive to the ionic strength of the assembly medium; both the aggregation and colchicine binding inhibition induced by GSH are inhibited at higher ionic strength. These results indicate a very complex interaction of GSH with tubulin.     

Organization of Methanobacterium thermoautotrophicum bacteriophage psi M1 DNA

Summary M1 is a virulent bacteriophage of Methanobacterium thermoautotrophicum strain Marburg. Restriction enzyme analysis of the linear, 30.4 kb phage DNA led to a circular map of the 27.1 kb M1 genome. M1 is thus circularly permuted and exhibits terminal redundancy of approximately 3 kb. Packaging of M1 DNA from a concatemeric precursor initiates at the pac site which was identified at coordinate 4.6 kb on the circular genome map. It proceeds clockwise for at least five packaging rounds. Headful packaging was also shown for M2, a phage variant with a 0.7 kb deletion at coordinate 23.25 on the map.     

A sensitive and continuous fluorometric assay for phospholipase A2 using pyrene-labeled phospholipids in the presence of serum albumin

Phospholipase A2 activity can be determined fluorometrically in the presence of serum albumin using phospholipids labeled at the sn-2-acyl position with 10-pyrenyldecanoic acid. In the water reaction medium 10-pyrene phospholipids form vesicles and the monomer fluorescence of the pyrene is negligible due to pyrene-pyrene interaction. Upon phospholipid hydrolysis 10-pyrenyldecanoic acids are produced and tightly bind to albumin so that a monomer pyrene fluorescence is observed. We obtained an excellent parallelism between hydrolysis determined by a classical extraction method and that followed by direct and continuous spectrofluorometric recording of the monomer emission of pyrene. This assay can measure picomole amounts of phospholipids hydrolyzed per minute so that picogram quantities of phospholipases A2 from pancreas or from venoms can be measured. Phospholipase activity remains proportional to enzyme concentration over three orders of magnitude. The method can be used to quantify the phospholipase A2 activity of crude extracts of low specific activity.