Utilize este identificador para referenciar este registo: https://hdl.handle.net/10316/10294
Título: Modulation of sarcoplasmic reticulum calcium pump activity by membrane fluidity
Autor: Almeida, Leonor M. 
Vaz, Winchil L. C. 
Zachariasse, Klaas A. 
Madeira, Vítor M. C. 
Data: Set-1984
Editora: American Chemical Society
Citação: Biochemistry. 23:20 (1984) 4714-4720
Resumo: Intramolecular excimerization of 1,3-di- l-pyrenylpropane [Py(3)Py] was used to assess the fluidity of sarcoplasmic reticulum membranes (SR); on the basis of the spectral data, the probe incorporates completely inside the membrane probably somewhere close to the polar head groups of phospholipid molecules, however not in the very hydrophobic core. The excimerization rate is very sensitive to lipid phase transitions, as revealed by thermal profiles of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) bilayers. Cholesterol abolishes pretransitions and broadens the thermal profiles of the main transitions which vanish completely at 50 mol % sterol. Excimer formation in liposomes of SR total lipid extracts does not show any sharp transitions, as in the case of DMPC and DPPC. However, the plots display discontinuities at about 20 OC which are broadened by cholesterol and not observed at 50 mol % sterol. Also cholesterol has been incorporated in native SR membranes by an exchange technique allowing progressive enrichment without changing the phospholipid/protein molar ratio. As in liposomes, discontinuities of excimer formation at 20 OC are broadened by cholesterol enrichment. The full activity of uncoupled Ca*+-ATPase is only affected by cholesterol above a molar ratio to phospholipid of 0.4. However, a significant decrease in activity (about 20%) is only noticed at a ratio of 0.6 (the highest technically achieved); at this ratio, about 28 lipid molecules per CaZ+-ATPase are expected to be relatively free from cholesterol interaction. The vesicle structure is still intact at this high ratio, as judged from the absence of basal activity (not Ca2+ stimulated). However, the sterol significantly decreases to about 60% the energetic efficiency of Ca2+ pumping (CaZ+/ATP ratio).
URI: https://hdl.handle.net/10316/10294
ISSN: 0006-2960
DOI: 10.1021/bi00315a029
Direitos: openAccess
Aparece nas coleções:FCTUC Ciências da Vida - Artigos em Revistas Internacionais

Ficheiros deste registo:
Ficheiro Descrição TamanhoFormato
Modulation of Sarcoplasmic Reticulum Ca2+-Pump.pdf859.99 kBAdobe PDFVer/Abrir
Mostrar registo em formato completo

Citações SCOPUSTM   

35
Visto em 26/fev/2024

Citações WEB OF SCIENCETM
5

35
Visto em 2/jan/2022

Visualizações de página 50

435
Visto em 26/mar/2024

Downloads

301
Visto em 26/mar/2024

Google ScholarTM

Verificar

Altmetric

Altmetric


Todos os registos no repositório estão protegidos por leis de copyright, com todos os direitos reservados.