So adjacent to the SRP receptor is a protein channel known as the translocan. And the translocan is normally closed. But upon binding of the SRP ribosome complex to the SRP receptor on the er membrane, the channel opens up. And at this point, the synthesis of the growing polypeptide chain commences. So it basically resumes and the growing polypeptide chain will extend into the endoplasmic reticular lumen of that organelle. So basically, in step number one, our free ribosome synthesizes the signal sequence that is found at the beginning of the growing polypeptide chain.