State of aggregation of detergent-solubilized sarcoplasmic reticulum adenosine triphosphatase investigated by...

The state of aggregation of purified sarcoplasmic reticulum adenosine triphosphatase (ATPase) was investigated by high-performance liquid chromatography (LKB TSK-G 4000 SW column) in the presence of various detergents: sodium dodecylsulphate, dodecyl octaethylene glycol monoether (C12E8), sodium deoxycholate, Triton X-100 and myristoylglycerophosphocholine. When the protein (5 mg ml-1) was solubilized with detergent (2 mg per mg protein) and the column was equilibrated with 1 mg ml-1 of the respective detergent, a molecular weight for the monomeric ATPase protein ranging from 100,000 to 200,000 was obtained. In addition to the monomeric form, significant amounts (more than 20%) of aggregated ATPase protein were observed when C12E8 or deoxycholate was used. These results are in agreement with the observation of a great tendency for self-aggregation of the ATPase protein in conventional gel filtration chromatography and ultracentrifugation experiments. The dimeric form of the ATPase protein was detected only when deoxycholate and, probably, when C12E8 was used.