Lac repressor binds as a tetramer to two operators.

TLS Online TPP Program

#Id: 7785

#Unit 2. Cellular Organization

These proteins contain a nuclear-localization signal (NLS) that directs their selective transport into the  nucleus.

TLS Online TPP Program

#Id: 7786

#Unit 2. Cellular Organization

NLSs were first discovered through the analysis of mutations of the gene for large T-antigen encoded by simian virus 40 (SV40).

TLS Online TPP Program

#Id: 7787

#Unit 2. Cellular Organization

The wild-type form of large T-antigen is localized to the nucleus in virus-infected cells, whereas some mutated forms of large T-antigen accumulate in the cytoplasm.

TLS Online TPP Program

#Id: 7788

#Unit 2. Cellular Organization

The mutations responsible for this altered cellular localization occur within a specific seven-residue sequence rich in basic amino acids near the C-terminus of the protein: Pro-Lys-Lys-Lys-Arg-Lys-Val.

TLS Online TPP Program

#Id: 7789

#Unit 2. Cellular Organization

Nuclear transport receptor

A general class of proteins that facilitate protein transport into or out of the nucleus by binding to a nuclear import sequence or a nuclear export sequence

TLS Online TPP Program

#Id: 7790

#Unit 2. Cellular Organization

Nuclear transport receptor

have affinity for FG-repeats on nucleoporins.