Two Mechanisms Down-Regulate Signaling from RTKs

1. Phosphotyrosine phosphatases

2. Receptor-mediated endocytosis followed by degradation in lysosomes

TLS Online TPP Program

#Id: 7936

#XL - Q Biochemistry

The SRP is made up of six proteins bound to a 300-nucleotide RNA, which acts as a scaffold for the hexamer.

TLS Online TPP Program

#Id: 7935

#XL - Q Biochemistry

The SRP is a cytosolic ribonucleoprotein particle that transiently binds to both the ER signal sequence in a nascent protein and the large (60S) ribosomal subunit, forming a large complex.

TLS Online TPP Program

#Id: 7934

#XL - Q Biochemistry

The two key components in protein targeting in ER:

Signal recognition particle (SRP)

SRP receptor

TLS Online TPP Program

#Id: 7933

#XL - Q Biochemistry

Signal sequences

contain one or more positively charged amino acids adjacent to a continuous stretch of 6–12 hydrophobic residues (known as the hydrophobic core)

TLS Online TPP Program

#Id: 7932

#XL - Q Biochemistry

Signal sequence

ER targeting sequence, located at the N-terminus of the protein

TLS Online TPP Program

#Id: 7931

#XL - Q Biochemistry

Microsomes

when cells are homogenized, the rough ER breaks up into small closed vesicles with ribosomes on the outside