How are proteins imported into the thylakoids of chloroplast

How are proteins imported into the thylakoids of chloroplasts?

Solution

Answer:

Nuclear-encoded thylakoid proteins are first imported into the chloroplast and then directed to the thylakoid using different sorting mechanisms.

The proteins targeted for chloroplasts contain transit peptide sequence called stromal import sequence or a stromal and thylakoid targeting sequence.

Import receptors and translocation complexes aid in targeting the protein to its respective location. The endoproteases in stroma remove transit peptide sequences and the proteins fold into functional form.

Proteins of the outer membrane complex are called Tocs

Inner membrane translocon complex proteins are called Tics

Proteins destined for thylakoid membrane will have both stromal and thylakoid targeting sequence. cpSRP pathway is used for the insertion of these integral membrane proteins into the thylakoid membrane.