Characterization and in vitro processing of transfer RNA precursors accumulated in a temperature-sensitive mutant of Escherichia coli

1978 ◽  
Vol 123 (3) ◽  
pp. 287-326 ◽  
Author(s):  
Hitoshi Sakano ◽  
Yoshiro Shimura
Keyword(s):  
Escherichia Coli ◽  
Transfer Rna ◽  
Temperature Sensitive ◽  
Sensitive Mutant ◽  
Temperature Sensitive Mutant ◽  
In Vitro Processing

Directionality of microtubule assembly: an in vivo study with the ciliate Tetrahymena

1978 ◽  
Vol 33 (1) ◽  
pp. 227-234
Author(s):  
S.F. Ng
Keyword(s):  
Tetrahymena Thermophila ◽  
Recessive Gene ◽  
Microtubule Assembly ◽  
In Vivo Study ◽  
Temperature Sensitive ◽  
Sensitive Mutant ◽  
Posterior Portion ◽  
Temperature Sensitive Mutant

A temperature-sensitive mutant homozygous for the recessive gene molb in Tetrahymena thermophila offers opportunity for studying the direction of microtubule assembly in vivo. At 39 degrees C the mutant fails to divide properly; the 2 daughter animals remain attached and bend over each other. As revealed by protargol staining, the bending results in acute turning and breaking of some of the longitudinal microtubular bands close and parallel to the surface. Hence, 2 broken microtubular ends are available for study of the problem of directionality of microtubule assembly, by assessing which of the 2 ends regenerates. In most cases the posterior portion of the longitudinal microtubular band regenerates. The present study hence supports the conclusion based on in vitro observation in other systems that microtubule assembly is predominantly unidirectional.

scholarly journals AnEscherichia coliMutant Defective in Lipid Export

2001 ◽  
Vol 276 (15) ◽  
pp. 11461-11464 ◽  
Author(s):  
William T. Doerrler ◽  
Mary C. Reedy ◽  
Christian R. H. Raetz
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Outer Membrane ◽  
Abc Transporter ◽  
Temperature Sensitive ◽  
Sensitive Mutant ◽  
Lipid Trafficking ◽  
Temperature Sensitive Mutant ◽  
Inner Surface ◽  
Membrane Region

Escherichia coliphospholipids and lipopolysaccharide, made on the inner surface of the inner membrane, are rapidly transported to the outer membrane by mechanisms that are not well characterized. We now report a temperature-sensitive mutant (WD2) with an A270T substitution in a trans-membrane region of the ABC transporter MsbA. As shown by32Piand14C-acetate labeling, export of all major lipids to the outer membrane is inhibited by ∼90% in WD2 after 30 min at 44 °C. Transport of newly synthesized proteins is not impaired. Electron microscopy shows reduplicated inner membranes in WD2 at 44 °C, consistent with a key role for MsbA in lipid trafficking.

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