Binds immobilized fibronectin. Component of the cytoskeleton-like structure which stabilizes the shape of the wall-less mycoplasma. This cytoskeleton-like network of accessory proteins containing HMW proteins 1 to 5 allows the proper anchoring of cytadhesin proteins in the mycoplasmal membrane at the attachment organelle. Essential for successful surface parasitism (By similarity). Localizes specifically to the attachment membrane. Runs as a smaller protein in high passage extracts (passage 164) versus low passage (passage 14) that shares the same N-terminus. Sequencing has shown this smaller version to be due to an internal 54 bp deletion.