Protein Transport into Mitochondria

Protein Transport into Mitochondria


Hello frnds in this videos we will be discussing
abt Protein Transport into Mitochondria……….. we know Most of the proteins destined for
mitochondria are synthesised in the cytosol and then these proteins are transported into
the mitochondria … and for this transport to occur the Proteins
contain Signal Sequences , where to get transported in Mitochondria , like in Matrix or in Inner
membrane space ….. or intermemebarne space ….
We know the mitochondria is a double membrane organelle and in both of these membranes the
Protein Import Channels or pores are installed to facilitate the PROTEIN TRANSPORT…….AND
the proteins which drive the transport are TRANSLOCONS….. for both of the membranes
there are different translocons present…. First we see there is a TOM complex,,,that
is the Translocon of Outer Membarne then we have TIM complex which is the Translocon
of INNER membrane,…..both of these protein channels drive the Protein import,,,,,, the Most important outer membrane translocon
is TOM 40…and there are other accessory outer translocons like TOM 20/22 and tom 70…..
but TOM 40 is the main chain pore…. and for inner membrane translocons we see
there are TIM 23/17,,tim 44,,,tim 54…tim 22,,,,,tim 9/10 and ever translocon exists
in different pathways….. like we see TIM 54 and tim 22 facilitate transport
into Inner mito membrane,,,,, along with tim 9 10 apart from these complexes there is another
transport molecule which is OXA 1,,,,,,it is a protein transport channel which facilitates
Transport from Mito Matrix to Inner mito membrane….. this OXA 1 acts as Mitochondrial inner membrane
insertase; mediates the insertion of both mitochondrial- and nuclear-encoded proteins
from the matrix into the inner membrane; ….basically when the protein molecules c
ontain both the sequences , that is Matrix targeting sequences and OXA targeting sequences
,,, then at that time , the protein molecules is first transported to matrix where then
it is taken into Inner membrane by OXA 1 …………now lets see in detail the Patway for protein
transport ….. first of all we will see the the Pathway for
Protein Import into Mitochondrial Matrix…… we have mitochondria with Outer membrane having
Import receptor,,,,which will recognise the Matrix Targeting sequences…..and also there
is inner mitochondrial membrane barrier for transport….. the precursor protein to be transported has
C terminus and N terminus ends……and the matrix targeting sequences are present on
the n terminus end of protein…… to ensure that the precursor proteins remains
in unfolded state the cytosolic HSC 70 molecules bind to the protein and keeps the molecules
in unfolded state…..just remember that the Cytosolic HSC 70 has different function than
matrix HSC 70,, ,,which we will find later on what this matrix
hsc 70 does…….and it is not HSP 70 ,,,,,,, and this process needs energy which is supplied
by the Hydrolysis of ATP………….. then this protein molecule matrix targeting sequences
binds to Import receptor on outer membrane …which then targets this protein molecules
into Channel pore of TOM 40… now protein molecule needs to get through
the inner membrane and for that the inner membrane has got Translocons in the form of
TIM 23 17 and tim 44 … The translocating protein then moves through
Inner membrane channels and it is by the help of matrix HSC 70 , which pulls the protein
inside and helps in getting the protein into the matrix with the energy from ATP molecules….. now the protein is in matrix and here the
MPP,,,matrix processing proteasee cleaves the tartgeting sequence from the rest of protein
molecylkels,,, which then starts folding into its functional form , either by Chaperoning
or auto auto folding…and finally we get the active protein in mito matrix….. so
this is how proteins destined for moto matrix are transported , through these channels,,,,,,,,,
in the next part of video we will be discussing OXA 1 and other pathways