2.  Elongation

★The second and the next aminoacyl-tRNA inline bind to the ribosome along with GDP and elongation factor.

★It consists of the following steps:

  · 进位(entrance/registration)

  · 转肽(transpeptidation)

  · 移位(translocation)

  Initiation complex+elongation factor+ GTP +Mg2+

★Elongation Factorsrequiredfor peptide polymerization

Elongation factor	function
EF-Tu	Transferring aminoacyl-tRNA to A site, GTPase activity（转移氨基酸，水解GTP）
EF-Ts	Replace GDP to bind Tu
EFG	Translocase activity(转位酶活性)

★Elongation又称注册(registration)

★Correct aminoacyl-tRNA entersA site.

★EF-T functions in entrance (prokaryote） 

（2）Peptide bond formation

    Transpeptidase(转肽酶) catalyze the formation of peptide bond.

                                      Large subunit：rRNA + rproteins

（3）Leave（E site）

（4）Translocation(转位): EF-G has translocase  activity, which catalyzes movement of peptidyl-tRNA from A site to P site. 

Peptide chain elongation