We have used monoclonal antibodies developed against the apolipoproteins associated with pulmonary surfactant purified from rabbit lavage fluid to study the expression of epitopes common to these proteins. The pulmonary surfactant contained nearly 20 proteins, of which at least 10 were not derived from serum. Electrophoresis, with sulfhydryl reduction of these proteins indicated apparent molecular weights of ~155, 135, 125, and 115 x 103 (high-molecular-weight group); 80, 70, and 60 x 103 (intermediate group); and 18 through 10 x 103 (low-molecular-weight group). Two-dimensional polyacrylamide gel electrophoresis, in which the proteins were electrophoresed without reduction in the first dimension, but with sulfhydryl reduction in the second dimension, revealed that the 80, 70, and 60 x 103 proteins dissociated into proteins of nominal molecular weights of 40, 35, and 30 x 103, respectively. In contrast, the 125 and 115 x 103 proteins of the high-molecular-weight group contained a protein which could only be reduced to a minimum molecular weight of 55 to 60 x 103. Monoclonal antibodies generally were of three types: 1) those that reacted strongly with the high-molecular-weight group and weakly with the intermediate group; 2) those that reacted conversely; and 3) those that reacted only with the low-molecular-weight group. Our results indicate that at least two different surfactant apolipoproteins, with differing minimum molecular weights in SDS-polyacrylamide gel electrophoresis, have common epitopes. Although these results cannot certify a physiological relationship between these proteins, they suggest that the intracellular synthesis or extracellular processing of surfactant apolipoproteins may be more complicated than predicted by the findings of previous experiments, perhaps involving the posttranslational assembly of one surfactant protein into oligomers which resist dissociation under the conditions used for the analyses.
|Original language||English (US)|
|Journal||American Journal of Physiology - Cell Physiology|
|State||Published - Jan 1 1986|
ASJC Scopus subject areas
- Cell Biology