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

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

Quizplus · Accepted Answer

In contrast to other outer membrane proteins, the abundant ?-barrel proteins of the outer mitochondrial membrane require the SAM complex for their correct integration, following TOM-mediated import into the intermembrane space. Just one signal sequence is enough for targeting to the matrix, and it forms an amphiphilic helix. Prior to import, mitochondrial proteins are kept unfolded in the cytosol by chaperones.

Indicate True (T) and False (F) Statements Below Regarding the Mitochondrial