Blobel Image removed due to copyright reasons Messenger rna Microsomes Ribosomes Cytoplasmic RER vesicles) Extracts charged tRNAs
Cytoplasmic Extracts N Messenger RNA Ribosomes & charged tRNAs Microsomes (RER vesicles) in vitro Blobel Image removed due to copyright reasons
M essage e N Ribosomes++ + tRNAs Microsomes Purifie extract added late added early Protein in Protein in Protein in Protein in lumen of supernatent supernatent supernatent microsomes
+ added late + + + added early - - Purified extract Microsomes - + + + + + Message Ribosomes tRNAs Protein in supernatent Protein in lumen of microsomes Protein in supernatent N Protein in supernatent
Nobel laureate, 1999 Gunter blobel Image removed due to copyright reasons From the previous experiment, Blobel demonstrated that the amino acid sequence at the beginning(N terminus) of exported proteins is recognized y a complex This complex is required to get the protein into the lumen of Er o get into the lumen of the er the protein has to be just beginning to be translate Since not all exported proteins have the same N terminus, blobel predicted, like Millstein, whatever the sequence was, it would be later cleaved
From the previous experiment, Blobel demonstrated that the amino acid sequence at the beginning (N terminus) of exported proteins is recognized by a complex. This complex is required to get the protein into the lumen of ER. To get into the lumen of the ER the protein has to be just beginning to be translated. Since not all exported proteins have the same N terminus, Blobel predicted, like Millstein, whatever the sequence was, it would be later cleaved. Gunter Blobel Nobel Laureate, 1999 Image removed due to copyright reasons
Bacterium Eukaryotic Cell N 20 amino acids Hydrophobic amino acids Signal Sequence
+ Hydrophobic amino acids N ~20 amino acids 5’ “Signal Sequence” Bacterium Eukaryotic Cell N N
Signal Signal recognition Sequence Particle SRP
N SRP Signal Sequence Signal Recognition Particle