Mitochondria- TIM Flashcards
Which type of proteins does TIM23 recognise
proteins with an internal amphipathic helical presequence- matrix soluble proteins
Which Tim protein is responsible for sorting proteins with a matrix targeting signal followed by a hydrophobic sequence and where are these proteins destined for
tim23sort. these proteins are destined for IM integration
what is the role of TIM22
translocates proteins with an internal presequence dedicated to metabolite carrier family proteins
How do Tim23 and TIM17 work together
they form a cation selective voltage gated channel in the membrane. Tim17 regulates pore opening
what is the role o TIM50
it has a domain which sticks into the inter membrane space and binds the prescience of proteins emerging from TOM22. it also helps to close the TIM23 channel
what is the role of TIM21
links TIM and TOM by interacting with TOM22’s I’m space domain. It is also responsible for dissociating TIM23 from PAM
what does the PAM complex stand for
presequence associated motor complex
which subunits comprise PAM
Tim44, mtHSP70, Mge1, pam18, pam16 and pam17
what is the role of tim44
binds to translocating polypeptide as it exits the TIM complex
what is the role of mtHSP70
it binds TIM44 and the translocating peptide. it also hydrolyses ATP, energising translocation and aiding translocation through a pulling and trapping mechanism
what is the role of mge1
it is a nucleotide exchange factor for Hsp70
what is the role of Pam18
stimulates aptness activity of Hsp70
what is the role of PAM16
controls pam18 mechanism
what is the role of pam17
organises the PAM complex
How does Tim23 optimise targeting of proteins to either the membrane or the matrix
interacts with partners for example recruits cytochrome bc1 and cytochrome oxidase complex leading to delta psi dependent integration of the protein into the inner membrane
which Tim proteins comprise the Tim complex which translocates proteins with an internal presequences
Tim22, Tim54, Tim18, Tim12
what is the role of Tim54
it is analogous to TIm50 and binds the proportion and other translocase proteins
what is the role of tim18
involved in dynamics, assembly and interaction with other components
what is the role of tim12
link between tim22 and small tim 9/10
describe the stages of import of mitochondrial ATP/ADP related carrier proteins through the Tim22 complex
it is delivered to TOM70 receptor and passed onto TOM 20/22. interaction occurs between Tom70 and duplicated internal targeting sequences. the protein is released in an ATP dependent manner to GIP and inserted into the general insertion pore of which TOM40 is the main component. it then interacts with tim9/10. tim9/10 interacts with tim12 and tim22 and the protein is inserted into tim22 pore. under high membrane potential the protein exits tim22 and dimerises in the membrane to form the active functional protein
describe the role/importance of delta psi in translocation of proteins that are inserted into the IM of the mitochondria
it;s electrophoretic effect on the presequence is required for import and insertion and it also regulates the opening of the channels
describe the common structure of small time 8-13
they contain a conserved twin CXXXC motif and fold by forming 2 disulphide bonds between cysteine residues of 2 of these motifs and they assemble in 70da hecamers.
what are the components of the small tim hexameter which chaperones carrier proteins
3xsmall tim 9 and 3x small tim 10
what are the components of the small tim hexameter which chaperones proteins translocated through the Tim23 complex
3x 8 and 3 x13
which small tim is membrane bound
tim12
describe the import and folding of small tims into the mitochondrial IM space
they are imported via TOM40 complex then folded by a disulphide relay system catalysed by Mia40 and Erv1. Mia40 oxidises the imported protein and is itself reduced via disulphide bond exchange. Ev1 reoxidises Mia40 so cycle can repeat and Erv1 is deoxidised by donating electrons to cytC which donates electrons to the electron transport chain
how are proteins with a C term presequence such as DNA helicase Hmi1 translocated
in the same manner however it occurs in Cterm to N term direction. this demonstrates polarity is not important
how is fumarase dual targeted to the mitochondria and cytosol
transport is initiated into the mitochondria where the presequence is cleaved. some proportion of the protein is then released back into the cytosol
how are mitochondrially encoded proteins inserted into the IM
via the Oxa pathway. Oxa1p interacts with ribosomes cotranslationally
