Interactions of proteins with ganglioside-enriched microdomains on the membrane: The lateral phase separation of molecular species of GD1a ganglioside, having homogeneous long-chain base composition, is recognized by Vibrio cholerae sialidase

M. Masserini, P. Palestini, B. Venerando, A. Fiorilli, D. Acquotti, G. Tettamanti

Research output: Contribution to journalArticlepeer-review

Abstract

The thermotropic behavior (studied by high-sensitivity differential scanning calorimetry) and susceptibility to Vibrio cholerae sialidase hydrolysis of large unilamellar vesicles of dipalmitoylphosphatidylcholine, containing native GD1a ganglioside or the molecular species of GD1a containing C18:1 or C20:1 long-chain base (C18:1 GD1a; C20:1 GD1a), were studied. Vesicles containing ganglioside (10% in molar terms) showed the presence in the heat capacity function of a second minor peak besides the phospholipid main transition peak. The presence of a second peak is much more evident with C20:1 GD1a than with C18:1 GD1a, the difference being potentiated by Ca2+ and indicating a different tendency of the GD1a molecular species to undergo lateral phase separation. The scans of vesicles containing native GD1a showed the features of those obtained with C18:1 GD1a and C20:1 GD1a, indicating that the main components of native GD1a, C18:1 GD1a and C20:1 GD1a, maintain their individual aggregative properties. V. cholerae sialidase affects vesicle-bound GD1a at a much higher rate (17-25-fold) than it does micellar GD1a, the activation by Ca2+ being 3- and 2-fold, respectively. The Vmax values were identical on C18:1 GD1a and C20:1 GD1a in micellar dispersions, whereas they were markedly higher (from 20 to 50%) on C18:1 GD1a than on C20:1 GD1a in vesicular dispersions. Exhaustive sialidase hydrolysis of vesicles carrying native GD1a produced C18:1 GM1 and C20:1 GM1 in the same proportion as the C18:1 and C20:1 species present in native GD1a (53.9% and 46.1%). Conversely, sialidase treatment producing about 10% of GD1a hydrolysis gave origin to C18:1 GM1 and C20:1 GM1 in the proportions of 65-69% and 31-35%, indicating the preference by the enzyme to affect C18:1 GD1a. These data show that V. cholerae sialidase is able to recognize GD1a molecules with different long-chain base moieties on the basis of their tendency to undergo lateral phase separation on the membrane, realizing higher Vmax values of the substrate molecules more dispersed on the surface.

Original languageEnglish
Pages (from-to)7973-7978
Number of pages6
JournalBiochemistry
Volume27
Issue number20
Publication statusPublished - 1988

ASJC Scopus subject areas

  • Biochemistry

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