TAMU BIOL 213 - Protein Transportation (6 pages)

Previewing pages 1, 2 of 6 page document View the full content.
View Full Document

Protein Transportation



Previewing pages 1, 2 of actual document.

View the full content.
View Full Document
View Full Document

Protein Transportation

380 views


Lecture number:
19
Pages:
6
Type:
Lecture Note
School:
Texas A&M University
Course:
Biol 213 - Molecular Cell Biol
Edition:
1
Unformatted text preview:

BIOL 213 1st Edition Lecture 19 Outline of Last Lecture I Somatic cells and gametes II The five basic types of genetic change that contribute to evolution a Mutation within a gene b Gene duplication c Gene deletion d Exon shuffling e Horizontal gene transfer III Gene duplication a Gene families IV Genome duplication V VI Exon shuffling can result in the appearance of eukaryotic genes Transposable elements can change genes by inserting new coding sequences VII VIII a Can transpose exons Horizontal gene transfer a Plasmids The human genome IX Comparative genomics X Overview a Gene duplication b Exon shuffling These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c Transposable elements d Horizontal gene transfer Outline of Current Lecture I The fate of proteins after synthesis compartmentalization II Protein sorting a Necessary and sufficient III Transport through nuclear pores IV Transport across membranes a Mitochondria and chloroplast b ER membrane i Soluble proteins ii Transmembrane proteins V Transport by vesicles a Highly specific Current Lecture I The fate of proteins after synthesis compartmentalization a After proteins are translated they must be transported throughout the cell and sometimes outside of the cell b Each protein has a specific target location c This is called compartmentalization d Eukaryotes are compartmentalized by their membrane bound organelles Compartment Cytosol Nucleus ER Golgi Lysosomes Main function Metabolic pathways protein synthesis Contains main genome DNA RNA synthesis Synthesis of most lipids protein distribution Protein and lipid modification for distribution Intracellular degradation Endosomes Mitochondria Chloroplasts Peroxisomes II III Sorting of endocytosed materials ATP synthesis oxidative phosphorylation Photosynthesis Oxidation of toxic compounds contains peroxide Protein sorting a Each protein must have a signal sequence of amino acids on its end that is unique to the organelle to which it needs to be transported i These sequences are necessary and sufficient for protein sorting 1 Necessary they are needed the proteins will not be sorted without them 2 Sufficient they are all that is needed the proteins don t need anything else to be sorted b There are three main energy dependent ways in which a protein is transferred from the cytosol into an organelle c Transport through nuclear pores i Seen in the nucleus d Transport across membranes e Transport by vesicles Transport through nuclear pores a The nucleus has two membranes b These pores allow molecules through both membranes c These pores have fibril molecules on both sides of the membrane to prevent unwanted materials from diffusing through i The fibril molecules on the nuclear side create a nuclear cage that catch unwanted materials d Small molecules can diffuse through the pores without any help e But proteins are too big to diffuse by themselves they are transported by helper proteins i They need the appropriate sorting signal sequence nuclear localization signal 1 This is a short stretch of lysines and arginines that are positively charged ii They are helped by nuclear transport receptors helper proteins iii When a protein with the correct signal sequence approaches the nucleus a nuclear transport receptor will bind to it iv The two proteins will move through the nuclear pore into the nucleus v Once inside the nucleus a Ran GTP binds to the nuclear transport receptor causing the transported protein to be released inside the nucleus IV vi The Ran GTP nuclear transport receptor complex travels back outside the nucleus vii The complex is GTP hydrolyzed this is the energy input that causes this kind of transport to be active and the now Ran GDP and nuclear transport receptor dissociate viii The Ran GDP travels back into the nucleus ix The nuclear transport receptor is ready to transport another protein f This transport is active energy input is required i GTP g The proteins stay completely folded during the transportation Transport across membranes a Mitochondrial and chloroplast i The signal sequence of the protein binds to the receptor protein that is integrated in the mitochondrial chloroplast membrane ii The receptor protein diffuses through the membrane until it comes in contact with a pore that spans across both membranes iii The protein will unfold as it goes through the pore because the pore is so small iv Once it s inside the mitochondria chloroplast chaperonins refold it 1 They refold it so that it has a specialized function specific to the organelle 2 When it s in the cytosol it doesn t have a specific function because it s folded differently v The signal sequence is cleaved so that the protein is now mature b ER i Most proteins that are inside the ER lumen are to be transported outside the cell ii These are synthesized into the lumen iii After they are in the lumen the proteins can be stabilized by disulfide bridges between two cysteines 1 This is because the ER lumen is an oxidizing environment whereas the cytosol is a reducing environment 2 The oxidizing environment will cause the sulfur to bind to a sulfur atom instead of a hydrogen atom 3 The sulfur atom is more electronegative than the hydrogen causing the sulfur to be oxidized iv Soluble proteins 1 When a ribosome reaches the signal sequence during protein synthesis a signal recognition particle SRP will bind to the signal sequence causing the ribosome to stop synthesizing V a The signal sequence is at the end of a polypeptide chain of a soluble protein 2 The SRP will bind to an SRP receptor in the ER membrane which is next to a translocation channel 3 The SRP will transfer the polypeptide chain to the channel and then dissociate 4 The signal sequence will remain in the channel and the ribosome will continue to synthesize the protein through the channel and into the lumen so that a loop of polypeptide chain forms within the lumen 5 Once the protein is complete the signal sequence will be cleaved by signal peptidase causing it to stay in the channel while the protein moves completely into the lumen v Transmembrane proteins 1 When a ribosome reaches the signal sequence during protein synthesis a signal recognition particle SRP will bind to the signal sequence causing the ribosome to stop synthesizing a The signal sequence is in the middle of a polypeptide chain of a protein 2 The SRP will bind to an SRP receptor in the


View Full Document

Access the best Study Guides, Lecture Notes and Practice Exams

Loading Unlocking...
Login

Join to view Protein Transportation and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Protein Transportation and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?