Mitochondrial protein targeting

A short review of protein targeting more specifically mitochondrial protein targeting i.e. post-translational translocation

1. Name - Ipsita Sahoo Reg no- 200705180160 Guided by- Mr. Gagan Kumar Panigrahi School of Applied Science, CUTM, BBSR M Sc. 1st year Zoology Subject- Cell and Molecular Biology Topic - “Mitochondrial Protein Targeting” Session- 2020-22

2. Introduction Overview of Protein targeting Protein Import Into Mitochondrial Matrix Protein transport from cytosol to inner mitochondrial membrane Protein transport from cytosol to mitochondrial inter-membrane space Conclusion Reference CONTENTS

3. Introduction Protein targeting or protein sorting is a biological mechanism by which proteins are transported to their appropriate destinations i.e. within or outside the cell . Since the translation of mRNA into protein by a ribosome takes place within the  cytosol , proteins destined for secretion or a specific organelle must be translocated .  This process can occur during translation, known as co-translational translocation, or after translation is complete, known as post-translational translocation .

4. Overview of Protein targeting

5. Protein targeting to Mitochondria Mitochondrial proteins are synthesized by 80S cytosolic as well as 70S matrix ribosome. About 99% of mitochondrial proteins are encoded by nuclear gene and are synthesized as precursors on cytosolic-ribosomes . Proteins synthesized by cytosolic - ribosomes are translocated into mitochondria post- translationally . Inter membrane space

6. Requirement of Mitochondrial protein import Mitochondrial protein import requires translocation complexes that mediate translocation and mitochondrial targeting signal (MTS) sequences. Translocation Complexes Two distinct translocation complex are situated in outer and inner mitochondrial membranes referred to as TOM ( Translocase of the outer membrane) complex and TIM ( Translocase of the inner membrane) complex. b) Mitochondrial Targeting Signal

7. Protein Import Into Mitochondrial Matrix Most of matrix targeting proteins enter into mt matrix contain N-terminal cleavable targeting sequences & synthesized by cytosolic 80S.

8. Protein transport from cytosol to inner mt membrane

9. Protein transport from cytosol to mitochondrial inter-membrane space

10. Proteins sorted to mitochondrial destinations other than the matrix usually contain two or more targeting sequences, one of which may be an N-terminal matrix-targeting Sequence. Some mitochondrial proteins destined for the inter-membrane space or inner membrane are first imported into the matrix and then redirected; others never enter the matrix but go directly to their final location. Conclusion

11. Reference Nelson DL (January 2017).  Lehninger principles of biochemistry . Cox, Michael M.,, Lehninger , Albert L. (Seventh ed.). New York, NY.  ISBN   978-1-4641-2611-6 .  OCLC   986827885 . Sommer MS, Schleiff E (August 2014).  "Protein targeting and transport as a necessary consequence of increased cellular complexity" .  Cold Spring Harbor Perspectives in Biology .  6  (8): a016055.  doi : 10.1101/cshperspect.a016055 .  PMC   4107987 .  PMID   25085907 . Walter P, Ibrahimi I, Blobel G (November 1981).  "Translocation of proteins across the endoplasmic reticulum. I. Signal recognition protein (SRP) binds to in-vitro-assembled polysomes synthesizing secretory protein" .  The Journal of Cell Biology .  91  (2 Pt 1): 545–50.  doi : 10.1083/jcb.91.2.545 .  PMC   2111968 .  PMID   7309795 . Lodish H, Berk A, Kaiser C, Krieger M, Bretscher A, Ploegh H, Amon A, Martin K (2008).  Molecular Cell Biology  (8th ed.). New York: W.H. Freeman and Company. pp. 591–592.  ISBN   978-1-4641-8339-3 .