A membrane fraction (MF2) has been purified from isolated microvilli of the MAT-C1 subline of the 13762 rat mammary ascites adenocarcinoma under conditions which cause F-actin depolymerization. This membrane preparation contains actin as a major component, although no filamentous structures are observed by transmission electron microscopy. Membranes were extracted with a Triton X-100-containing actin-stabilizing buffer (S buffer) or actin-destabilizing buffer (D buffer). In D buffer greater than 90% of metabolically labeled protein and glycoprotein was extracted, and 80-90% of these labeled species was extracted in S buffer. When S buffer extracts of MF2 were fractionated by either gel filtration on Sepharose 6 B or rate-zonal sucrose density gradient centrifugation, most of the actin was found to be intermediate in size between G- and F-actin. In D buffer most of the MF2 actin behaved as G-actin. Extraction and gel filtration of intact microvilli in S buffer also showed the presence of the intermediate form of actin, indicating that it did not arise during membrane preparation. When [35S]methionine-labeled G-actin from ascites cells was added to S buffer extracts of MF2 and chromatographed, all of the radioactivity chromatographed as G-actin, indicating that the intermediate form of actin did not result from an association of G-actin molecules during extraction or chromatography. The results of this study suggest that the microvillar membrane fraction is enriched in an intermediate form of actin smaller than F-actin and larger than G-actin.
Article| September 01 1982
Membrane-associated actin from the microvillar membranes of ascites tumor cells.
K L Carraway,
K L Carraway
R F Cerra
C A Carraway
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1982) 94 (3): 624–630.
K L Carraway, R F Cerra, G Jung, C A Carraway; Membrane-associated actin from the microvillar membranes of ascites tumor cells.. J Cell Biol 1 September 1982; 94 (3): 624–630. doi: https://doi.org/10.1083/jcb.94.3.624
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