LIFE SCIENCE

Detailed explanation-1: -Like all GTPases, Ran exists in two different states: either GTP-bound or GDP-bound. Depending on the nucleotide bound, Ran interacts with several different proteins, most of which have well defined roles in nucleocytoplasmic transport ([1, 2] and references therein).

Detailed explanation-2: -During mitosis, the Ran cycle is involved in mitotic spindle assembly and nuclear envelope reassembly after the chromosomes have been separated. During prophase, the steep gradient in RanGTP-RanGDP ratio at the nuclear pores breaks down as the nuclear envelope becomes leaky and disassembles.

Detailed explanation-3: -Ran plays a key role in controlling nucleocytoplasmic trafficking, a process in which many accessory proteins involved in nuclear import and export pathways have also been implicated. It is clear that RanGTPase is crucial for both the nuclear import and export processes.

Detailed explanation-4: -Import cycle First step of the nuclear transport cycle is the formation of importin-cargo complex. Importins can bind cargo molecules after recognition of their NLSs.

Detailed explanation-5: -RAN (ras-related nuclear protein) is a small GTP binding protein belonging to the RAS superfamily that is essential for the translocation of RNA and proteins through the nuclear pore complex. The RAN protein is also involved in control of DNA synthesis and cell cycle progression.