The amphipathic helix of an enzyme that regulates phosphatidylcholine synthesis remodels membranes into highly curved nanotubules.
Biochim Biophys Acta
; 1818(5): 1173-86, 2012 May.
Article
em En
| MEDLINE
| ID: mdl-22285779
ABSTRACT
CTPphosphocholine cytidylyltransferase (CCT) is an amphitropic protein regulating phosphatidylcholine synthesis. Lipid-induced folding of its amphipathic helical (AH) membrane-binding domain activates the enzyme. In this study we examined the membrane deforming property of CCT in vitro by monitoring conversion of vesicles to tubules, using transmission electron microscopy. Vesicle tubulation was proportional to the membrane density of CCT and proceeded either as growth from a pre-formed surface bud, or as a global transformation of roughly spherical vesicles into progressively thinner tubules. The tubulation pathway depended on the lipid compositional heterogeneity of the vesicles, with heterogeneous mixtures supporting the bud-extension pathway. Co-existence of vesicles alongside thick and thin tubules suggested that CCT can discriminate between flat membrane surfaces and those with emerging curvature, binding preferentially to the latter. Thin tubules had a limiting diameter of ~12nm, likely representing bilayer cylinders with a very high density of 1 CCT/50 lipids. The AH segment was necessary and sufficient for tubulation. AH regions from diverse CCT sources, including C. elegans, had tubulation activity that correlated with α-helical length. The AH motifs in CCT and the Parkinson's-related protein, α-synuclein, have similar features, however the CCT AH was more effective in its membrane remodeling function. That CCT can deform vesicles of physiologically relevant composition suggests that CCT binding to membranes may initiate deformations required for organelle morphogenesis and at the same time stimulate synthesis of the PC required for the development of these regions.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Caenorhabditis elegans
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Colina-Fosfato Citidililtransferase
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Proteínas de Caenorhabditis elegans
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Nanotubos
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Membranas Artificiais
Limite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2012
Tipo de documento:
Article