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SINTESIS PROTEIN Sri Puji Astuti Wahyuningsih FST UNAIR     BIODAS II Dept. Biologi FST UNAIR.

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Presentasi berjudul: "SINTESIS PROTEIN Sri Puji Astuti Wahyuningsih FST UNAIR     BIODAS II Dept. Biologi FST UNAIR."— Transcript presentasi:

1 SINTESIS PROTEIN Sri Puji Astuti Wahyuningsih FST UNAIR     BIODAS II Dept. Biologi FST UNAIR

2 ARUS INFORMASI GENETIK Informasi DNA adalah dalam bentuk urutan tertentu dari nukleotida di sepanjang untai DNA DNA diwariskan oleh organisme ◦ Menghasilkan ciri-ciri tertentu melalui sintesis protein Proses di mana DNA mensintesis protein dinamakan ekspresi gen ◦ Ada dua tahapan, yaitu transkripsi dan translasi BIODAS II Dept. Biologi FST UNAIR

3 RIBOSOM ◦ Adalah organel sel yang menfasilitasi terjadinya translasi (sintesis polipeptida) Figure 17.1 BIODAS II Dept. Biologi FST UNAIR

4 Konsep 1: GEN MENENTUKAN PROTEIN MELALUI TRANSKRIPSI DAN TRANSLASI 1909, Dokter Inggris Archibald Garrod ◦ Adalah orang pertama yang menunjukkan bahwa gen menentukan fenotip melalui enzim yang mengkatalisis reaksi kimia tertentu dalam sel 1920, Beadle dan Edward Tatum: Neurospora crassa (kapang roti) yang dimutasi dengan sinar-X ◦ Menciptakan mutan yang tidak bisa bertahan hidup pada media minimal ◦ Mengembangkan hipotesis "satu gen-satu enzim“ ◦ Fungsi gen adalah untuk menentukan produk enzim tertentu BIODAS II Dept. Biologi FST UNAIR

5 PRINSIP DASAR TRANSKRIPS DAN TRANSLASI Transkripsi ◦ Adalah sintesis RNA di bawah arahan DNA ◦ Menghasilkan messenger RNA (mRNA) atau RNA duta Translasi ◦ Adalah sintesis polipeptida yang terjadi di bawah arahan mRNA ◦ Terjadi dalam ribosom BIODAS II Dept. Biologi FST UNAIR

6 Pada Prokariota ◦ Transkripsi dan translasi terjadi bersamaan (translasi mRNA dimulai saat transkripsi masih berlangsung) Figure 17.3a Prokaryotic cell. In a cell lacking a nucleus, mRNA produced by transcription is immediately translated without additional processing. (a) TRANSLATION TRANSCRIPTION DNA mRNA Ribosome Polypeptide BIODAS II Dept. Biologi FST UNAIR

7 Pada Eukariota ◦ Transkrip RNA atau transkrip primer atau pre-mRNA dimodifikasi sebelum menjadi mRNA Figure 17.3b Eukaryotic cell. The nucleus provides a separate compartment for transcription. The original RNA transcript, called pre-mRNA, is processed in various ways before leaving the nucleus as mRNA. (b) TRANSCRIPTION RNA PROCESSING TRANSLATION mRNA DNA Pre-mRNA Polypeptide Ribosome Nuclear envelope BIODAS II Dept. Biologi FST UNAIR

8 Aliran informasi genetik adalah ◦ DNA  RNA  protein Aliran Informasi Genetik ◦ Dikodekan sebagai urutan triplet basa yang tidak tumpang tindih yang disebut kodon BIODAS II Dept. Biologi FST UNAIR

9 Selama transkripsi ◦ Gen menentukan urutan basa di sepanjang molekul mRNA Figure 17.4 DNA molecule Gene 1 Gene 2 Gene 3 DNA strand (template) TRANSCRIPTION mRNA Protein TRANSLATION Amino acid ACC AAACCGAG T UGG U UU G GC UC A Trp Phe Gly Ser Codon BIODAS II Dept. Biologi FST UNAIR

10 KODE GENETIK Kodon dalam mRNA ◦ Diterjemahkan menjadi asam amino atau berfungsi sebagai sinyal mulai (start) dan berhenti (stop) dari translasi Figure 17.5 Second mRNA base UCA G U C A G UUU UUC UUA UUG CUU CUC CUA CUG AUU AUC AUA AUG GUU GUC GUA GUG Met or start Phe Leu lle Val UCU UCC UCA UCG CCU CCC CCA CCG ACU ACC ACA ACG GCU GCC GCA GCG Ser Pro Thr Ala UAU UAC UGU UGC TyrCys CAU CAC CAA CAG CGU CGC CGA CGG AAU AAC AAA AAG AGU AGC AGA AGG GAU GAC GAA GAG GGU GGC GGA GGG UGG UAA UAG Stop UGA Stop Trp His Gln Asn Lys Asp Arg Ser Arg Gly U C A G U C A G U C A G U C A G First mRNA base (5 end) Third mRNA base (3 end) Glu BIODAS II Dept. Biologi FST UNAIR

11 Komponen Molekular Transkripsi Sintesis RNA dikatalisis oleh RNA polimerase. Berfungsi untuk memisahkan untai DNA dan menghasilkan nukleotida RNA dari arah 5’  3’ Prokariota hanya mempunyai 1 jenis RNA polimerase. Eukatiota memiliki 3 jenis RNA polimerase, yang digunakan untuk sintesis mRNA adalah RNA polimerase II Konsep 2: TRANSKRIPSI ADALAH SINTESIS RNA YANG DIARAHKAN DNA BIODAS II Dept. Biologi FST UNAIR

12 Sintesis Transkrip RNA Tahapan transkripsi ◦ Inisiasi ◦ Elongasi ◦ Terminasi Figure 17.7 Promoter Transcription unit RNA polymerase Start point Rewound RNA transcript 3 3 Completed RNA transcript Unwound DNA RNA transcript Template strand of DNA DNA 1 Initiation. After RNA polymerase binds to the promoter, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand. 2 Elongation. The polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5  3. In the wake of transcription, the DNA strands re-form a double helix. 3 Termination. Eventually, the RNA transcript is released, and the polymerase detaches from the DNA. BIODAS II Dept. Biologi FST UNAIR

13 Pengikatan RNA Polimerase dan Inisiasi Transkripsi Promotor : sekuen DNA tempat melekatnya RNA polimerase dan tempat inisiasi untuk sintesis RNA Faktor Transkripsi ◦ Membantu RNA polimerase untuk mengenali sekuen promoter pada Eukariota Figure 17.8 TRANSCRIPTION RNA PROCESSING TRANSLATION DNA Pre-mRNA mRNA Ribosome Polypeptide TATAA A A ATATTTT TATA box Start point Template DNA strand Transcription factors Promoter RNA polymerase II Transcription factors RNA transcript Transcription initiation complex Eukaryotic promoters 1 Several transcription factors 2 Additional transcription factors 3 BIODAS II Dept. Biologi FST UNAIR

14 Elongation RNA polymerase Non-template strand of DNA RNA nucleotides 3 end C A E G C A A U T A G G T T A A C G U A T C A T CCA A T T G G Newly made RNA Direction of transcription (“downstream”) Template strand of DNA BIODAS II Dept. Biologi FST UNAIR

15 Elongasi Transkripsi RNA polimerase bergerak sepanjang DNA ◦ Enzim menguraikan DNA double helix, sekitar basa DNA dibuka dan dibaca untuk menghasilkan pasangannya, yaitu nukleotida RNA Terminasi Transkripsi RNA polimerase telah selesai membaca DNA. Telah dihasilkan seluruh untaian nukleotida RNA BIODAS II Dept. Biologi FST UNAIR

16 Konsep 3: SEL EUKARIOTIK MEMODIFIKASI RNA SETELAH TRANSKRIPSI Enzim di inti sel pada eukariotik ◦ Modifikasi pre-mRNA dengan cara tertentu sebelum pesan genetik dikirim ke sitoplasma BIODAS II Dept. Biologi FST UNAIR

17 Pengubahan ujung mRNA Setiap ujung molekul pre-mRNA dimodifikasi dengan cara tertentu ◦ Ujung 5 dimodifikasi dengan penambahan nukeotida tudung (cap) ◦ Ujung 3 dengan penambahan ekor poli-A Figure 17.9 A modified guanine nucleotide added to the 5 end 50 to 250 adenine nucleotides added to the 3 end Protein-coding segment Polyadenylation signal Poly-A tail 3 UTR Stop codonStart codon 5 Cap 5 UTR AAUAAA AAA…AAA TRANSCRIPTION RNA PROCESSING DNA Pre-mRNA mRNA TRANSLATION Ribosome Polypeptide G P PP 5 3 BIODAS II Dept. Biologi FST UNAIR

18 Split Genes dan RNA Splicing Penyambungan RNA / RNA splicing ◦ Memindahkan intron dan menggabungkan exon Figure TRANSCRIPTION RNA PROCESSING DNA Pre-mRNA mRNA TRANSLATION Ribosome Polypeptide 5 Cap Exon Intron Exon Intron Exon 3 Poly-A tail Introns cut out and exons spliced together Coding segment 5 Cap UTR Pre-mRNA mRNA BIODAS II Dept. Biologi FST UNAIR

19 Dilakukan oleh spliceosome, yaitu enzim yang berfungsi untuk memindahkan intron dan menggabungkan exon Figure RNA transcript (pre-mRNA) Exon 1 Intron Exon 2 Other proteins Protein snRNA snRNPs Spliceosome components Cut-out intron mRNA Exon 1 Exon BIODAS II Dept. Biologi FST UNAIR

20 Fungsi dan Pentingnya Intron Adanya intron ◦ Memungkinkan satu gen dapat mengkode lebih dari satu jenis polipeptida BIODAS II Dept. Biologi FST UNAIR

21 Protein sering memiliki arsitektur modular ◦ Terdiri dari daerah struktural dan fungsional yang disebut domain ◦ Kode exon akan berbeda untuk domain yang berbeda pada protein Figure Gene DNA Exon 1 Intron Exon 2IntronExon 3 Transcription RNA processing Translation Domain 3 Domain 1 Domain 2 Polypeptide BIODAS II Dept. Biologi FST UNAIR

22 Konsep 4: TRANSLASI ADALAH SINTESIS POLIPEPTIDA YANG DIARAHKAN OLEH RNA Komponen Molekular Translasi Sel mentranslasi pesan mRNA menjadi protein d engan bantuan RNA transfer (tRNA) BIODAS II Dept. Biologi FST UNAIR

23 Konsep Dasar Translasi Figure TRANSCRIPTION TRANSLATION DNA mRNA Ribosome Polypeptide Amino acids tRNA with amino acid attached Ribosome tRNA Anticodon mRNA Trp Phe Gly A G C A AA C C G U G GUUU GG C Codons 5 3 BIODAS II Dept. Biologi FST UNAIR

24 Struktur dan Funsi RNA Transfer Molekul tRNA ◦ Tersusun dari untai RNA tunggal yang panjangnya hanya sekitar 80 nukleotida ◦ Berbentuk L A C C Figure 17.14a Two-dimensional structure. The four base-paired regions and three loops are characteristic of all tRNAs, as is the base sequence of the amino acid attachment site at the 3 end. The anticodon triplet is unique to each tRNA type. (The asterisks mark bases that have been chemically modified, a characteristic of tRNA.) (a) 3 C C A C G C U U A A G ACA C C U * G C * * G UGU * C U * GA G G U * * A * A A G U C A G A C C * C GA G A G G G * * G A C U C * A U U U A G G C G 5 Amino acid attachment site Hydrogen bonds Anticodon A BIODAS II Dept. Biologi FST UNAIR

25 Figure 17.14b (b) Three-dimensional structure Symbol used in this book Amino acid attachment site Hydrogen bonds Anticodon A AG (c) BIODAS II Dept. Biologi FST UNAIR

26 Enzim aminoacyl-tRNA synthetase ◦ Menggabungkan masing-masing asam amino ke tRNA yang benar Figure Amino acid ATP Adenosine Pyrophosphate Adenosine Phosphates tRNA PPP P P PiPi PiPi PiPi P AMP Aminoacyl tRNA (an “activated amino acid”) Aminoacyl-tRNA synthetase (enzyme) Active site binds the amino acid and ATP. 1 ATP loses two P groups and joins amino acid as AMP. 2 3 Appropriate tRNA covalently Bonds to amino Acid, displacing AMP. Activated amino acid is released by the enzyme. 4 BIODAS II Dept. Biologi FST UNAIR

27 Subunit ribosomal ◦ Disusun oleh protein dan molekul RNA yang dinamakan RNA ribosomal atau rRNA Figure 17.16a TRANSCRIPTION TRANSLATION DNA mRNA Ribosome Polypeptide Exit tunnel Growing polypeptide tRNA molecules E P A Large subunit Small subunit mRNA Computer model of functioning ribosome. This is a model of a bacterial ribosome, showing its overall shape. The eukaryotic ribosome is roughly similar. A ribosomal subunit is an aggregate of ribosomal RNA molecules and proteins. (a) 5 3 Ribosom ◦ Menfasilitasi ikatan antikodon tRNA dengan kodon mRNA selama sintesis protein BIODAS II Dept. Biologi FST UNAIR

28 Ribosom mempunyai 3 sisi pengikatan (binding sites) tRNA ◦ Sisi P ◦ Sisi A ◦ Sisi E Figure 17.16b EPA P site (Peptidyl-tRNA binding site) E site (Exit site) mRNA binding site A site (Aminoacyl- tRNA binding site) Large subunit Small subunit Schematic model showing binding sites. A ribosome has an mRNA binding site and three tRNA binding sites, known as the A, P, and E sites. This schematic ribosome will appear in later diagrams. (b) BIODAS II Dept. Biologi FST UNAIR

29 Figure 17.16c Amino end Growing polypeptide Next amino acid to be added to polypeptide chain tRNA mRNA Codons 3 5 Schematic model with mRNA and tRNA. A tRNA fits into a binding site when its anticodon base-pairs with an mRNA codon. The P site holds the tRNA attached to the growing polypeptide. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. Discharged tRNA leaves via the E site. (c) BIODAS II Dept. Biologi FST UNAIR

30 Pembentukan Polipeptida Kita dapat membagi translasi menjadi 3 tahapan ◦ Inisiasi ◦ Elongasi ◦ Terminasi BIODAS II Dept. Biologi FST UNAIR

31 Asosiasi Ribosom dan Inisiasi Translasi Tahap inisiasi translasi ◦ Menyatukan mRNA, tRNA yang membawa asam amino pertama dari polipeptida, dan dua subunit ribosom Large ribosomal subunit The arrival of a large ribosomal subunit completes the initiation complex. Proteins called initiation factors (not shown) are required to bring all the translation components together. GTP provides the energy for the assembly. The initiator tRNA is in the P site; the A site is available to the tRNA bearing the next amino acid. 2 Initiator tRNA mRNA mRNA binding site Small ribosomal subunit Translation initiation complex P site GDP GTP Start codon A small ribosomal subunit binds to a molecule of mRNA. In a prokaryotic cell, the mRNA binding site on this subunit recognizes a specific nucleotide sequence on the mRNA just upstream of the start codon. An initiator tRNA, with the anticodon UAC, base-pairs with the start codon, AUG. This tRNA carries the amino acid methionine (Met). 1 Met U A C A U G EA Figure BIODAS II Dept. Biologi FST UNAIR

32 Elongasi Translasi ◦ Asam amino ditambahkan satu per satu ke asam amino sebelumnya Figure Amino end of polypeptide mRNA Ribosome ready for next aminoacyl tRNA E PA E P A E P A E P A GDP GTP GDP 2 2 site 5 3 TRANSCRIPTION TRANSLATION DNA mRNA Ribosome Polypeptide Codon recognition. The anticodon of an incoming aminoacyl tRNA base-pairs with the complementary mRNA codon in the A site. Hydrolysis of GTP increases the accuracy and efficiency of this step. 1 Peptide bond formation. An rRNA molecule of the large subunit catalyzes the formation of a peptide bond between the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site. This step attaches the polypeptide to the tRNA in the A site. 2 Translocation. The ribosome translocates the tRNA in the A site to the P site. The empty tRNA in the P site is moved to the E site, where it is released. The mRNA moves along with its bound tRNAs, bringing the next codon to be translated into the A site. 3 BIODAS II Dept. Biologi FST UNAIR

33 Terminasi Translasi Tahap akhir translasi adalah ketika ribosom sampai kodon stop pada mRNA Figure Release factor Free polypeptide Stop codon (UAG, UAA, or UGA) When a ribosome reaches a stop codon on mRNA, the A site of the ribosome accepts a protein called a release factor instead of tRNA. 1 The release factor hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. The polypeptide is thus freed from the ribosome. 23 The two ribosomal subunits and the other components of the assembly dissociate. BIODAS II Dept. Biologi FST UNAIR

34 Poliribosom Sejumlah ribosom dapat mentranslasi satu molekul mRNA tunggal secara simultan. Hanya pada sel prokariota Figure 17.20a, b Growing polypeptides Completed polypeptide Incoming ribosomal subunits Start of mRNA (5 end) End of mRNA (3 end) Polyribosome An mRNA molecule is generally translated simultaneously by several ribosomes in clusters called polyribosomes. (a) Ribosomes mRNA This micrograph shows a large polyribosome in a prokaryotic cell (TEM). 0.1 µm (b) BIODAS II Dept. Biologi FST UNAIR

35 Protein Fungsional Rantai polipeptida /protein menjalani modifikasi setelah proses translasi Protein dimodifikasi - untuk membentuk molekul tiga dimensi / folding (pelipatan) - Untuk dapat ditranfer ke lokasi yang membutuhkan BIODAS II Dept. Biologi FST UNAIR

36 Protein dibutuhkan dalam sistem endomembran (contoh: enzim lisosim yang ada di organel lisosom) atau disekresikan (contoh: enzim pencernaan seperti amilase). Protein harus ditransport ke retikulum endoplasma (ER) Signal peptida pada ribosom binding pada signal-recognition particle (SRP). Kompleks keduanya binding pada protein reseptor SRP di ER BIODAS II Dept. Biologi FST UNAIR

37 Figure Ribosome mRNA Signal peptide Signal- recognition particle (SRP) SRP receptor protein Translocation complex CYTOSOL Signal peptide removed ER membrane Protein ERLUMEN Mekanisme signal untuk protein target pada ER Polypeptide synthesis begins on a free ribosome in the cytosol. 1 An SRP binds to the signal peptide, halting synthesis momentarily. 2 The SRP binds to a receptor protein in the ER membrane. This receptor is part of a protein complex (a translocation complex) that has a membrane pore and a signal-cleaving enzyme. 3 The SRP leaves, and the polypeptide resumes growing, meanwhile translocating across the membrane. (The signal peptide stays attached to the membrane.) 4 The signal- cleaving enzyme cuts off the signal peptide. 5 The rest of the completed polypeptide leaves the ribosome and folds into its final conformation. 6

38 Ringkasan transkripsi dan translasi pada sel eukariotik Figure TRANSCRIPTION RNA is transcribed from a DNA template. DNA RNA polymerase RNA transcript RNA PROCESSING In eukaryotes, the RNA transcript (pre- mRNA) is spliced and modified to produce mRNA, which moves from the nucleus to the cytoplasm. Exon Poly-A RNA transcript (pre-mRNA) Intron NUCLEUS Cap FORMATION OF INITIATION COMPLEX After leaving the nucleus, mRNA attaches to the ribosome. CYTOPLASM mRNA Poly-A Growing polypeptide Ribosomal subunits Cap Aminoacyl-tRNA synthetase Amino acid tRNA AMINO ACID ACTIVATION Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. Activated amino acid TRANSLATION A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome one codon at a time. (When completed, the polypeptide is released from the ribosome.) Anticodon A C C AAA U G G U U UA U G U A C E A Ribosome 1 Poly-A Codon BIODAS II Dept. Biologi FST UNAIR

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