Involvement of the C-terminal part of Pseudomonas fluorescens OprF in the modulation of its pore-forming properties.
Biochim Biophys Acta
; 1509(1-2): 237-44, 2000 Dec 20.
Article
em En
| MEDLINE
| ID: mdl-11118535
ABSTRACT
The major outer-membrane protein, OprF, from the psychrotrophic bacterium Pseudomonas fluorescens undergoes a reduction of its conductance value (from 250 pS to 80 pS) when the growth temperature is shifted from 28 degrees C to 8 degrees C. The involvement of changes in tertiary or quaternary structure in this behaviour, was implied by enzymatic digestion experiments in which OprFs purified from 8 degrees C and 28 degrees C cultures showed different accessibility to pronase. Resistant proteolytic fragments of 19 kDa, obtained from both OprF preparations, were identified as the N-terminal half of the native protein. These 19 kDa fragments induced ion channels in planar lipid bilayers with similar conductance values of 65-75 pS in 1 M NaCl, in contrast to the native proteins. Thus, the C-terminal part of the protein is required for the growth temperature-dependent modulation of OprF channel-forming properties. LPS was not detected on the proteolytic fragments while it was found in similar amounts on the native OprFs. These results suggest the LPS/porin association occurs through the C-terminal part of the porin. Radiolabelling experiments showed different phosphorylation levels of LPS for 8 degrees C and 28 degrees C cultures. Thus, in response to growth temperature, the structural modification of the LPS could be associated to the modulation of OprF pore size.
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Base de dados:
MEDLINE
Assunto principal:
Pseudomonas fluorescens
/
Porinas
Idioma:
En
Ano de publicação:
2000
Tipo de documento:
Article