Final answer:
The steps for the formation of an intermediate filament tetramer start with monomers forming a dimer, which then aligns in an antiparallel fashion to form a tetramer. These tetramers can then polymerize into filaments, providing structural support and elasticity to cells.
Step-by-step explanation:
The intermediate filaments play a crucial role in maintaining cell structure by resisting tension. They are unique among the cytoskeletal elements because they don’t possess enzymatic activity and lack polar ‘plus’ and ‘minus’ ends. The subunits of intermediate filaments begin as a pair of monomers that are created with globular domains at their terminal ends, linked by coiled rod regions. The formation of a tetramer follows several steps:
- Two monomers of intermediate filament proteins align side by side in a parallel fashion, forming a coiled-coil dimer.
- These dimers then align in a staggered antiparallel fashion, which leads to the formation of a tetramer, a structure composed of four monomers.
- The tetramers further assemble into intermediate filaments, forming a rope-like structure which contributes to cell rigidity and resistance to mechanical stress.
Intermediate filaments can also disassemble and reassemble during cell shape changes, and their elasticity is attributed to the coiled-rod regions that can stretch much like titin molecules. Moreover, intermediate filaments are involved in various cell structures and functions, including creating cell-to-cell junctions like desmosomes, and comprising elements of the nucleoskeleton, such as the nuclear lamina.