10 Protein Modification

POST-TRANSLATION (PROTEIN MODIFICATION)

MOLECULAR BIOLOGY (WEEK 10)

MODIFIKASI PROTEIN

Proses dimana ribosom menggunakan meng gunakan kode genetik u/ mentranslasi mentranslasi mRNA menjadi polipeptida. Setelah polipeptida disintesis, protein biasanya dimodifikasi sebelum menjadi ‘mature” dan protein aktif . Modifikasi ini dikenal dengan post

translational modification.

POST-TRANSLATION Polypeptide/protein transport ● Polypeptide/protein processing/m processing/modificatio odificatio ● Peptide deletion ●

Signal peptide removal( peptidases: trypsin, ● Activation by deletion trypsin, chymotryps chymotrypsin in)) ● Multisteps modification: insulin, penycyllin G acylase ● N terminal modification ● formil-residue removal (prokaryote) O O ● metionine-residue removal (eukaryote) ● C terminal modification HN CH C HN CH ● R -amino -amino acid modification H2 N   CH C R 1 R 2 R 3 ● phosphory  phosphorylation lation  phosphoserine ne → - cha charg rgee additio addition n ● phosphoseri  phosphotreonine treonine → + charge addition ● phospho  phosphotyrosine rosine → Ca2+ binding of casein ● phosphoty ● Carboxylation: ● asp → asp-COOH asp-COOH glu-COOH ● glu → glu-COOH ● methylation: lys → lys-methyl lys-methyl ● Glycosylation: ● addition of carbohydrate to asn, ser, thr → proteoglycan/glycoprotein ● addition of prosthethic (cofactor, coenzyme) groups:

O  

C

OH

addition to sytochrome asetil-CoA carboxylase addition of of biotin heme to C ● formation of disulfide bond → (native) conformation→protect from denaturation ● ●