Question

Which of the following proteins or protein complexes is directly required for the targeting of mitochondrial inner membrane multipass proteins, such as metabolite transporters, whose signal sequence is normally not cleaved after import?

1) TIM22
2) TIM23
3) OXA
4) Mia40
5) SAM

Answer 1

TIM22 is the protein complex that specifically targets mitochondrial inner membrane multipass proteins such as metabolite transporters, whose signal sequences are not cleaved after import.

Step-by-step explanation:

The correct protein complex responsible for the targeting of mitochondrial inner membrane multipass proteins, such as metabolite transporters with signal sequences that are typically not cleaved, is TIM22. The TIM22 complex is involved in the insertion and assembly of polytopic (multipass) proteins into the inner mitochondrial membrane, where they frequently function as transporters.

The process of mitochondrial protein import encompasses a series of steps and involves multiple proteins and complexes. For inner membrane multipass proteins, once they are delivered to the intermembrane space, TIM22 facilitates their integration into the mitochondrial inner membrane. This complex plays a pivotal role, distinct from other complexes like TIM23, which is mainly involved in importing matrix-targeted proteins with cleavable sequences, or OXA, which helps in the insertion of some inner membrane proteins synthesized within mitochondria.