Lecture #1 Flashcards by Heidi Deisher

what is the theory stating that an aerobic protobacterium was engulfed by an ancestral eukaryotic cell, conferring oxidative phosphorylation to the ancestral eukaryotic cell?

endosymbiotic theory

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what are invaginations in the inner membrane of the mitochondria

cristae

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what happens inside of cristae

oxidative phosphorylation

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where does the Krebs cycle, beta-oxidation, and steriodogenesis take place?

matrix

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what is the main characteristic that makes mitochondria unique?

they posses their own DNA

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how are mitochondria are derived?

from the production of membrane from the smooth ER and fission events of pre-existing organelles

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what is present on the inner mitochondrial membrane that is not present in the outer mitochondrial membrane?

cardiolipin

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how many polypeptides are derived from mitochondrial DNA?

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describe mitochondrial DNA:

16 kb circular dsDNA with several copies present

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what are the packing structures of mitochondrial DNA called?

nucleoids

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what does TFAM stand for?

transcription factor A mitochondrial

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what is mitochondrial DNA fully dependent on?

nuclear DNA

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why is mitochondrial dna fully dependent on nuclear dna?

the machinery needed for its replication, transcription, and translation comes from the nucleus

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what is the helicase responsible for unwinding mtDNA allowing for replication?

twinkle

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how are mitochondria configured in a cell?

in a elastic network where individual mitochondria are constantly fusing and dividing

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how many genes does mitochondrial DNA encode for?

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describe the two main parts of mitochondrial dna:

heavy strand (outer strand) and light strand (inner strand)

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where are the vast majority of genes coded for?

heavy strand

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what is the only gene transcribed by the light strand?

ND6

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mitochondrial DNA only has __ promotor, making it a _____________

1 ; polycistronic transcript

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where is the regulation of the abundance of the mitochondrial mRNA, tRNA, and rRNA established?

at the post-transcriptional level

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proteins encoded by mitochondrial DNA are all part of what?

the respiratory chain

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what characteristic of mitochondrial proteins does not allow them to be transported via the classical translocons?

they are the most hydrophobic proteins

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describe the 3’ end of mitochondrial DNA:

very short poly A tail

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what is unique about the 5' end in mitochondrial DNA?

no capping

what are the three main players in mitochondrial generation?

NRF-1&2 (nuclear respiratory factor), PPAr(alpha) and ERRs (estrogen-related receptors)

what is the key function of NRF-1&2?

important in the transcription of genes encoding for the subunits of the respiratory chain and for TFAM

what is the key function of PPAR(alpha)?

transctiption factor important for the control of the expression of genes of the fatty acid beta-oxidation

what is the key function of estrogen-related receptors?

control the TCA cycle genes, respiratory chain genes, and other oxidative phosphorylation-related genes

what is the main regulator of mitochondrial biogenesis?

PGC-1alpha

what occurs when PGC-1alpha is increased in both a transcriptional and protein level?

it binds to the key three transcription factors promoting both the transcription and translation of mitochondrial genes

what does PGC-1alpha promote besides the transcription and translation of mitochondrial DNA genes?

the transcription and translation of nuclear genes encoding for mitochondrial proteins

what are diseases caused by mutations in the mitochondrial DNA

primary mitochondrial diseases

besides mutations in mitochondrial dna, what can cause primary mitochondrial diseases?

mutations in nuclear genes encoding for mitochondrial proteins

how many pathways exist for the translation of proteins encoded by the nucleus?

three

one pathway for the translation of proteins encoded by the nucleus is mediated by what protein?

PUMILIO1

where does PUMILIO1 bind to?

3' end of specific mRNAs

what does PUMILIO1 allow for?

the co-translational import of proteins

how are the vast majority of nuclear encoded proteins imported?

in a post-translational manner and imported through chaperones

where is the vast majority of mitochondrial proteins synthesized?

cytosol

what are the 5 major protein import pathways into the mitochondria?

presequence, cystine rich, beta-barrels, carrier proteins, and alpha-helical proteins

what is a presequence?

aminoacidic sequence located in the N terminus

what is the function of a presequence?

unique target that allows for sorting

which specific types of proteins use the presequence pathways as their main form of transport?

matrix proteins and proteins residing in the inner membrane

for what specific types of proteins is a presequence most often NOT present?

proteins in the inner membrane space, outer membrane, and a few in the inner membrane

what specific type of bond can those proteins with cystine residues create?

disulphide bonds

where are the vast majority of proteins with cystein-residues folded? Therefore, what type of pre-sequence do they contain?

inside the ER; an ER pre-sequence

what do proteins that reside in the outer membrane not have?

pre sequences

what are beta-barrel proteins?

very large pores in the membrane that allow for the passage of solutes and ions

where are carrier proteins located?

inner mitochondrial membrane

if there is an alteration of the permeability of the imm, what occurs?

permeability transtion leading to apoptosis

what is the carrier protein passage dependent on?

mitochondrial membrane potential (MMP)

how long is the presequence of mitochondrial proteins?

15-50 amino acids

what does the presequence of mitochondrial proteins form?

an amphipathic alpha-helix

what recognizes the elements of the amphipathic alpha helix on the receptors of the omm?

translocons

what occurs when there is alteration of the permeability of the membrane?

permeability transition

what is the funcitonality of the imm very important for?

the mitochondrial membrane potential

what category does TOM 40 belong to?

beta-barrel proteins

what type of amino acids does TOM40 contain?

both hydophilic and hydrophobic

when approaching the omm where does the protein bind first, and then where does it enter after?

TOM20 then TOM40

what are the translocons of the inner mitochondrial membrane?

TIM complexes

a presequence is followed by a hydrophobic stretch, which signals for what?

signals for the protein to be laterally sorted into the inner membrane

describe the TIM23 SORT pathway:

related to the proteins that are highly hydrophobic and reside in the inner membrane

describe the TIM23 MOTOR pathway:

regards the proteins that are translocated into the matrix (aka the soluble proteins)

what is another name for mitochondrial membrane potential?

protonmotive force

what are the two components of the protonmotive force?

membrane potential and pH

what is the exact value of the mitochondrial membrane potential?

-180mV

what is used to measure the mmp in cells? And specifically, which one?

potential metric dyes ; TMRM

what is used to ensure that the mpp is being measured and not the plasma membrane potential instead?

uncouplers

what is an example of an uncoupler?

FCCP

what does the mitochondrial membrane potential directly activate on the imm?

TIM23 complex

what complex assists TIM23 in sorting a presequence-containing protein into the matrix?

presequence translocase-associated motor (PAM)

for those proteins containing a hydrophobic stretch, what serves as the gate keeper in TIM23 which allows them to be sorted laterally into the imm

Mgr2

what removes the presequence and folds a protein once it has entered into the mitochondrial matrix?

mitochondrial protease peptide (MPP)

what does the MPP do to proteins that have been translocated into the imm?

cleaves their presequences

what chaperone family is prevalent in the mitochondrial matrix that helps proteins fold?

Hsp60

where is Oxa1 located?

imm

what is the main function of Oxa1?

involved in the insertion of mtDNA-encoded proteins into the imm

what is the function of Oxa1 in regards to nuclear encoded proteins?

sorts proteins located on the imm that possess many transmembrane domains

what are the three main characteristics of carrier proteins?

they are very hydrophobic, contain 6 transmembrane domains, and do not have a presequence

what are the two main carrier proteins?

pyruvate carrier and ANT carrier

what are pyruvate and ANT carrier responsible for transporting across the inner membrane?

pyruvate, ATP, ADP

where are the only two places cysteine-rich precursors are found?

intermembrane space and the ER

what is the function of the MIA complex?

oxidizes cysteines in order to form a disulphide bond and allow a protein to reach its final folded conformation

which part of the MIA complex is responsible for carrying out the reaction to form the disulphide bond?

Mia40

the TOM40 channel is an example of which type of import protein?

beta-barrel protein

what is the most important metabolite channel of the outer membrane?

VDAC

describe VDAC:

voltage dependent, anion-selective channel important for the internalization of metabolites

what is the sorting and assembly machinery for the outer membrane which works in tandem with TOM40?

Sam50

what is responsible for inserting alpha-helical proteins into the omm?

MIM complexes