Nuclear pores are the communication gate between the nucleoplasm and the cytoplasm, and all transport between the two compartments occurs through them. Therefore, they are a key element in function, in the response to external signals and in the differentiation of cells. And this is because they condition, for example, the exit of messenger RNA to the cytoplasm, or the entry into the nucleus of transcription factors that determine gene expression.
The proteins that are part of the pore complex are called nucleoporins. In yeasts there are about 30 different nucleoporins in each nuclear pore, while in metazoans they can be 40 or more. But in the same pore there may be repeated proteins and this causes a pore of a mammalian cell to be formed by about 500 to 1000 total nucleoporins. The pore complex measures about 100 to 150 nm in diameter, with about 40 nm of useful internal diameter, and 50-70 nm in height. It is one of the largest protein complexes in the cell, with about 125,000 kDa molecular weight.
