Cytoplasmatic domain of Na,K-ATPase alpha-subunit is responsible for the aggregation of the enzyme in proteoliposomes.
We studied the thermal dependence of amide I' infrared absorption and fluorescence emission of Trp residues in the Na,K-ATPase of rabbit kidney. We studied the whole enzyme solubilized with detergent, the whole enzyme reconstituted in proteoliposomes and the protein fraction that remained in the lipid membrane after the trypsin digestion of the proteoliposomes. Cooperative unfolding and aggregation with increasing temperature were observed in the whole protein, whether solubilized or reconstituted, but not in the fraction remaining after trypsinization. The protein influenced the physical state of the lipid, decreasing the temperature of the gel to liquid-crystalline phase transition and the degree of cooperativity. This study provides new information for the understanding of the processes controlling the association mechanisms that are important for enzyme function in natural membranes.
FFCLRP-USP, Depto. Química, Ribeirão Preto, SP, Brazil.
Carolina Fortes
CF
Rigos
Hérica
H
de Lima Santos
Juliana Sakamoto
JS
Yoneda
Guillermo
G
Montich
Bruno
B
Maggio
Pietro
P
Ciancaglini
D000818:Animals; D003593:Cytoplasm / Q000201:enzymology; D007668:Kidney / Q000201:enzymology; D008055:Lipids / Q000737:chemistry; D044367:Phase Transition; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry*; D011510:Proteolipids; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D013696:Temperature; D014357:Trypsin / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry
D008055:Lipids; D021122:Protein Subunits; D011510:Proteolipids; C020485:proteoliposomes; D014364:Tryptophan; D014357:Trypsin; D000254:Sodium-Potassium-Exchanging ATPase