Creeping cells rely on molecular motors.For years, cell biologists have theorized that a migrating cell rolls along much like a military tank tread, pulling its outer membrane The outer membrane refers to the outside membranes of Gram-negative bacteria, the chloroplast, or the mitochondria. It is used to maintain the shape of the organelle contained within its structure, and it acts as a barrier against certain dangers. across its back in order to push its underside along. But a new study shows that the cell's ruffled ruf·fle 1 n. 1. A strip of frilled or closely pleated fabric used for trimming or decoration. 2. A ruff on a bird. 3. a. A ruckus or fray. b. Annoyance; vexation. 4. "leading edge" does most of the work, while the rest of the outer membrane remains fairly still. The researchers, led by Michael P. Sheetz at Duke University Medical Center in Durham, N.C., used laser "tweezers tweezers An instrument with pincers used to grasp or extract. See Optical tweezers. " to place tiny plastic beads on highly mobile cells taken from goldfish scales and cultured in the laboratory. In the Sept. 15 JOURNAL OF CELL BIOLOGY, they report that the beads on the cells' leading edges were swept rearward rear·ward 1 adv. Toward, to, or at the rear. adj. At or in the rear. n. A rearward direction, point, or position. rear as the cells advanced, while beads at the center of the cells' membranes showed only random movement. Sheetz and his colleagues say their finding suggests that a cell travels by "actively moving components of the cytoskeleton cytoskeleton System of microscopic filaments or fibres, present in the cytoplasm of eukaryotic cells (see eukaryote), that organizes other cell components, maintains cell shape, and is responsible for cell locomotion and for movement of the organelles within it. ," the cell's inner structural network. Unidentified molecular "motors" pull on the cell's cytoskeleton, the researchers propose, attaching to proteins at the membrane's leading edge and then heaving the cell forward without affecting other membrane regions. |
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