Time-resolved fluorescence of S-100a protein in the absence and presence of calcium and phospholipids.
We have used phase-modulation fluorescence lifetime measurements to study the single Trp residue of the Ca(2+)-binding protein S-100a. Trp fluorescence decay was not exponential for the protein irrespective of the absence or presence of Ca2+. Fluorescence decay was best described by Lorentzian lifetime distributions centered around two components (approx. 3 and 0.7 ns) for protein in absence of Ca2+ and one component (approx. 2.9 ns) for the protein in presence of 2 mM Ca2+. Similar studies were performed with S-100a interacting with cardiolipin, phosphatidylserine or egg phosphatidylcholine, both in absence and in presence of 2 mM Ca2+. Our data suggest that the conformation of the protein and its Ca(2+)-binding properties vary depending on the characteristics of charge and structure of phospholipids.
Zolese
G
G
Istituto di Biochimica, Facoltà di Medicina, Università di Ancona, Italy.
Giambanco
I
I
Curatola
G
G
De Stasio
G
G
Donato
R
R
D000818:Animals; D001923:Brain Chemistry; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D005454:Fluorescence Polarization; D010743:Phospholipids / Q000494:pharmacology*; D011487:Protein Conformation; D009418:S100 Proteins / Q000737:chemistry*; D014364:Tryptophan / Q000032:analysis*
D010743:Phospholipids; D009418:S100 Proteins; D014364:Tryptophan; D002118:Calcium