Question

Indicate true (T) and false (F) statements below regarding the mitochondrial protein import system. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTF.

( A) Mitochondrial proteins should fold natively twice: once in the cytosol and once inside the organelle.
( B) β-barrel proteins that are abundant in the mitochondrial outer membrane are imported from the cytosol independently of the TOM complex.
( C) Signal sequences that target precursor proteins to the mitochondrial matrix form an α- helix in which positively charged residues cluster near its N-terminus, while uncharged or hydrophobic residues cluster near the other side.
(D ) At least two signal sequences are required to direct proteins to the mitochondrial matrix.

Answer 1

The mitochondrial protein import system involves folding of proteins, import from the cytosol, and targeting to specific compartments.

Step-by-step explanation:

The correct answer would be TFFF.

1. Statement (A) is false. Mitochondrial proteins do not fold twice. They fold natively in the cytosol before being transferred to the mitochondria.
2. Statement (B) is true. β-barrel proteins in the mitochondrial outer membrane are indeed imported independently of the TOM complex.
3. Statement (C) is true. The signal sequences that target precursor proteins to the mitochondrial matrix form an α-helix with positively charged residues near the N-terminus and uncharged or hydrophobic residues near the other side.
4. Statement (D) is false. At least one signal sequence is required to direct proteins to the mitochondrial matrix, not two.