passages.id: BioInfer.d600.s0__text
passages.type: Sentence
passages.text: The core, isolated in the absence of free Ca2+, contains five major proteins: the actin (Mr 43 000) that makes up the filaments, the villin (Mr 95 000) and fimbrin (Mr 68 000) that cross-link the filaments together, and the 110 000 Mr polypeptide-calmodulin complex that makes up cross-filaments which project laterally from the core and link it to the inner surface of the microvillus membrane.