Question

Tom40 is a nuclear-encoded essential subunit of the TOM complex in the outer mitochondrial membrane. It is a β-barrel protein that forms the pore through which precursor proteins enter the intermembrane space from the cytosol. Indicate true (T) and false (F) statements below regarding the Tom40 protein. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF.

( A) Incorporation of new Tom40 in the outer membrane requires preexisting Tom40 in that membrane.
( B) Formation of new TOM complexes is dependent on the SAM complex.
( C) Tom40 is partially translocated through the outer membrane and is then transferred in the plane of the membrane to fold into its native conformation.
( D) Tom40 is translocated through the inner membrane as a precursor.

Answer 1

False, False, True, False

Step-by-step explanation:

Statement A: False. Incorporation of new Tom40 in the outer membrane does not require preexisting Tom40 in that membrane. Tom40 is newly synthesized and inserted into the outer membrane.

Statement B: False. Formation of new TOM complexes is not dependent on the SAM complex. The SAM complex is responsible for the assembly of the outer membrane beta-barrel proteins, while the TOM complex is responsible for the import of precursor proteins into the mitochondria.

Statement C: True. Tom40 is partially translocated through the outer membrane and then transferred in the plane of the membrane to fold into its native conformation.

Statement D: False. Tom40 is not translocated through the inner membrane as a precursor. It remains in the outer membrane of the mitochondria.