* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download protein synthesis overview
Alternative splicing wikipedia , lookup
Transcription factor wikipedia , lookup
Gene regulatory network wikipedia , lookup
Biochemistry wikipedia , lookup
List of types of proteins wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Bottromycin wikipedia , lookup
RNA interference wikipedia , lookup
Promoter (genetics) wikipedia , lookup
Molecular evolution wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Non-coding DNA wikipedia , lookup
RNA silencing wikipedia , lookup
Point mutation wikipedia , lookup
Expanded genetic code wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Genetic code wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Polyadenylation wikipedia , lookup
Gene expression wikipedia , lookup
Transfer RNA wikipedia , lookup
Messenger RNA wikipedia , lookup
PROTEIN SYNTHESIS OVERVIEW • RNA LINKS DNA’S GENETIC INSTRUCTIONS FOR MAKING PROTINS TO THE PROCESS OF PROTEIN SYNTHESIS • RNA COPIES (TRANSCRIBES) THE MESSAGE FROM DNA AND THEN TRANSLATES THAT MESSAGE INTO A PROTEIN • THE LINEAR SEQUENCE OF NUCLEOTIDES IN DNA DETERMINES THE LINEAR SEQUENCE OF AMINO ACIDS IN A PROTEIN • 3 STEPS: TRANSCRIPTION, RNA PROCESSSING, TRANSLATION VIDEO: PROTEIN SYNTHESIS OVERVIEW QuickTime™ and a Cine pak decomp ress or are nee ded to s ee this picture. NUCLEOTIDE TRIPLET CODONS • CODON = A THREE NUCLEOTIDE SEQUENCE IN mRNA THAT SPECIFIES WHICH AMINO ACID WILL BE ADDED TO THE GROWING POLYPEPTIDE CHAIN • READING FRAME = THE CORRECT GROUPING OF ADJACENT NUCLEOTIDE TRIPLETS INTO CODONS THAT ARE IN THE CORRECT SEQUENCE ON THE mRNA THE TRIPLET CODON DICTIONARY OF THE GENETIC CODE TRANSCRIPTION • TRANSCRIPTION = THE SYNTHESIS OF RNA USING DNA AS A TEMPLATE • TRANSCRIPTION OF MESSENGER (mRNA) FROM TEMPLATE DNA IS CATALYZED BY RNA POLYMERASES WHICH: – 1) SEPARATE THE TWO DNA STRAND AND LINK RNA NUCLEOTIDES AS THEY BASE-PAIR ALONG THE DNA TEMPLATE – 2) ADD NUCLEOTIDES ONLY TO THE 3’ END; THUS, mRNA MOLECULES GROW IN THE 5’ TO 3’ DIRECTIONS – ** TRANSCRIPTION OCCURS IN 3 STAGES: A) POLYMERASE BINDING AND INITIATION; B) ELONGATION; AND C) TERMINATION RNA POLYMERASE BINDING AND INIATION • RNA POLYMERASES BIND TO DNA AT REGIONS CALLED PROMOTERS • PROMOTERS = REGION OF DNA THAT INCLUDES THE SITE WERE RNA POLYMERASE BINDS AND WHERE TRANSCRIPTION BEGINS; ABOUT 100 NUCLEOTIDES LONG • TRANSCRIPTION FACTORS = DNA BINDING PROTEINS WHICH BIND TO SPECIFIC DNA NUCLEOTIDE SEQUENCES AT THE PROMOTER AND HELP RNA POLYMERASE RECOGNIZE AND BIND TO THE PROMOTER REGION SO TRANSCRIPTION CAN BEGIN ELONGATION OF RNA • ONCE TRANSCRIPTION BEGINS, RNA POLYMERASE II MOVES ALONG DNA AND PERFORMS TWO FUNCTIONS: • 1) IT UNTWISTS AND OPENS A SHORT SEGMENT OF DNA EXPOSING ABOUT TEN NUCLEOTIDE BASES; ONE OF THE EXPOSED DN STRAND IS THE TEMPLATE FOR BASEPAIRING WITH RNA NUCLEOTIDES • 2) IT LINKS INCOMING RNA NUCLEOTIDES TO THE 3’ END OF THE STRAND, THUS RNA GROWS ONE NUCLEOTIDE AT A TIME IN THE 5’ TO 3’ DIRECTION ELONGATION OF RNA • DURING TRANSCRIPTION, mRNA GROWS ABOUT 30 TO 60 NUCLEOTIDES PER SECOND. AS THE mRNA STRAND ELONGATES: – 1) IT PEELS AWAY FROM ITS DNA TEMPLATE – 2) THE NONTEMPLATE STRAND OF DNA REFORMS A DNA-DNA DOUBLE HELIX BY PAIRING WITH TEMPLATE STRAND – 3) SEVERAL RNA POLYMERASE II MOLECULES CAN SIMULANEOUSLY TRANSCRIBE THE SAME GENE; THUS, CELLS CAN PRODUCE PARTICULAR PROTEINS IN LARGE AMTS. TERMINATION OF TRANSCRIPTION • TRANSCRIPTION PROCEEDS UNTIL RNA POLYMERASE TRANSCRIBES A DNA SEQUENCE CALLED A TERMINATOR. THIS SIGNALS THE END OF THE TRANSCRIPTION PROCESS TRANSCRIPTION VIDEO QuickTime™ and a Cinepak decompress or are needed to s ee this picture. STAGES OF TRANSCRIPTION RNA PROCESSING • RNA TRANSCRIPTS IN EUKARYOTES ARE PROCESSED BEFORE LEAVING THE NUCLEUS TO YIELD FUNCTIONAL mRNA. THIS PROCESSING CAN BE DONE IN 2 WAYS: • 1) COVALENT ALTERATION OF BOTH THE 3’ AND 5’ ENDS • 2) REMOVAL OF INTERVENING SEQUENCES RNA PROCESSING • PRIMARY TRANSCRIPT = GENERAL TERM FOR INITIAL RNA TRANSCRIBED BY DNA • PRE-mRNA = PRIMARY TRANSCRIPT THAT WILL BE PROCESSED TO FUNCTIONAL MRNA ADDITION OF 5’ CAP • 5’ CAP = MODIFIED GUANINE NUCLEOTIDE THAT IS ADDED TO THE 5’ END OF MRNA SHORTLY AFTER TRANSCRIPTION BEGINS. IT HAS 2 IMPORTANT FUNCTIONS: • 1) PROTECTS THE GROWING mRNA FROM DEGRADATION BY HYDROLYTIC ENZYMES • 2) HELPS SMALL RIBOSOMAL SUBUNITS RECOGNIZE THE ATTACHMENT SITE ON mRNA’S 5’ END. A LEADER SEGMENT OF mRNA MAY ALSO BE PART OF THE RIBOSOME RECOGNITION SIGNAL • LEADER SEQUENCE = NONCODING (UNTRANSLATED) SEQUENCE OF mRNA FROM THE 5’ END TO THE START CODON ADDITION OF 5’ CAP AND POLY(A) TAIL ADDITION OF POLY(A) TAIL • THE 3’ END, WHICH IS TRANSCRIBED LAST, IS MODIFIED BY ENZYMATIC ADDITION OF A POLYA TAIL, BEFORE THE mRNA EXITS THE NUCLEUS • POLY(A) TAIL = SEQUENCE OF ABOUT 30 TO 200 ADENINE NUCLEOTIDES ADDED TO THE 3’ END OF mRNA – MAY INHIBIT DEGRADATION OF mRNA IN THE CYTOPLASM – MAY FACILITATE ATTACHMENT TO SMALL RIBOSOMAL SUBUNIT – MAY REGULATE PROTEIN SYNTEHSIS BY FACILITATING mRNA’S EXPORT FROM NUCLEUS – IS NOT DIRECTLY ATTACHED TO STOP CODON, BUT TO TRAILER SEGMENT • TRAILER SEQUENCE = NONCODING (UNTRANSLATED) SEQUENCE OF mRNA FROM THE STOP CODON TO THE POLY (A) TAIL RNA PROCESSING VIDEO QuickTime™ and a Cinepak decompress or are needed to s ee this picture. RNA SPLICING • GENES THAT CODE FOR PROTEINS IN EUKARYOTES MAY NOT BE CONTINUOUS SEQUENCES • INTRONS = NONCODING SEQUENCES IN DNA THAT INTERVENE BETWEEN CODING SEQUENCES; ARE TRANSCRIBED BUT NOT TRANSLATED • EXONS = CODING SEQUENCES OF A GENE THAT ARE TRANSCRIBED AND EXPRESSED RNA SPLICING • A PROCESS THAT REMOVES INTRONS AND JOINS EXONS IN PRE-mRNA; PRODUCES MATURE mRNA • snRNPS = SMALL NUCLEAR RIBONUCLEOPROTEINS; ARE INVOLVED IN mRNA SPLICING • SPLICEOSOME = A LARGE MOLECULAR COMPLEX THAT CATALYZES RNA SPLICING REACTIONS; MADE OF snRNPS AND OTHER PROTEINS SPLICEOSOMES • AS THE SPICEOSOME IS ASSEMBLED, ONE TYPE OF snRNP BASE PAIRS WITH A COMPLEMENTARY SEQUENCE AT THE 5’ END OF THE INTRON • THE SPLICEOSOME PRECISELY CUTS THE RNA TRANSCRIPT AT SPECIFIC SITES AT EITHER END OF THE INTRON, WHICH IS EXCISED • THE INTRON IS RELEASED AND THE ADJACENT EXONS ARE IMMEDIATELY SPLICED TOGETHER BY THE SPLICEOSOME RNA SPLICING ROLES OF snRNPs AND SPICEOSOMES IN mRNA SPLICING RIBOZYMES • OTHER KINDS OF RNA PRIMARY TRANSCRIPTS, SUCH AS THOSE GIVING RISE TO tRNA AND rRNA, ARE SPLICED BY MECHANISMS THAT DO NOT INVOLVE SPLICEOSOMES; HOWEVER, AS WITH mRNA SPLICING, RNA IS OFTEN INVOLVED IN CATALYZING THE REACTIONS • RIBOZYMES = RNA MOLECULES THAT CAN CATALYZE REACTIONS BY BREAKING AND FORMING COVALENT BONDS PROTEIN SYNTHESIS • IN A NUTSHELL, PROTEIN SYNTHESIS IS TAKING THE AMINO ACIDS FROM FOOD WE EAT AND LINKING THEM BACK INTO POLYPEPTIDES, PROTEINS THAT THE BODY USES FOR VARIOUS FUNCTIONS THROUGHOUT THE BODY VIDEO: PROTEIN SYNTHESIS OVERVIEW QuickTime™ and a Cine pak decomp ress or are nee ded to s ee this picture. TRANSLATION TRANSFER RNA (tRNA) • ALL TYPES OF RNA, INCLUDING tRNA, ARE TRANSCRIBED FROM TEMPLATE DNA • tRNA MUST TRAVEL FROM THE NUCLEUS TO THE CYTOPLASM FOR TRANSLATION • tRNA MOLECULES CAN BE REUSED tRNA STRUCTURE • tRNA IS A SINGLE-STRANDED RNA ONLY ABOUT 80 NUCLEOTIDES LONG • THE STRAND IS FOLDED, FORMING SEVERAL DOUBLE-STRANDED REGIONS WHERE SHORT BASE SEQUENCES OF HYDROGEN BOND WITH COMPLEMENTARY BASES • A SINGLE-PLACE VIEW SHOWS A CLOVER LEAF SHAPE • A LOOP PROTRUDES A ONE END OF THE L AND HAS A SPECIALIZED SEQUENCE OF 3 BASES CALLED THE ANTICODON • AT THE OTHER END OF THE L PROTRUDES THE 3’ END OF THE MOLECULE, THE ATTACHMENT SITE FOR AN AMINO ACID STRUCTURE OF tRNA WOBBLE EFFECT • THERE ARE ONLY ABOUT 45 TYPES OF tRNA, BUT THIS ENOUGH TO TRANSLATE THE 64 CODONS DUE TO THE WOBBLE EFFECT • WOBBLE EFFECT = THE ABILITYOF ONE tRNA TO RECOGNIZE 2 OR 3 DIFFERENT mRNA CODONS; THE THIRD BASE (5’ END) OF THE tRNA ANTICODON HAS SOME PLAY OR WOBBLE, SO THAT IT CAN HYDROGEN BOND WITH MORE THAN ONE KIND OF BASE IN THE 3RD POSITION (3’END) OF THE CODON • A SINGLE tRNA WITH THE ANTICODON CCG WILL RECOGNIZE THREE mRNA CODONS: GGU, GGC, GGA, ALL OF WHICH CODE FOR GLYCINE AMINOACYL-tRNA SYNTHETASES • A TYPE OF ENZYME THAT CATALYZES THE ATTACHMENT OF AN AMINO ACID TO ITS tRNA • EACH OF THE 20 A.A. HAS A SPECIFIC AMINOACYLtRNA SYNTHETASE • IN AN ENDERGONIC REACTION DRIVEN BY THE HYDROLYSIS OF ATP, A SYNTHETASE ATTACHES AN A.A. TO ITS tRNA IN 2 STEPS: – 1)ACTIVATION OF THE A.A. WITH AMP – 2) ATTACHMENT OF THE A.A. TO THE tRNA AN AMINOACYL-tRNA AT WORK THE ACTIVE SITE BIND THE A.A AND ATP; THE ATP LOSES 2 PHOSPHATES AND ATTACHES TO THE A.A. AS AMP THE tRNA COVALENTLY BONDS TO THE A.A, DISPLACING AMP RIBOSOMES • RIBOSOMES COORDINATE THE PAIRING OF tRNA ANTIOCODNS TO mRNA CODONS • RIBOSOMES HAVE 2 SUBUNITS (SMALL AND LARGE) WHICH ARE SEPARATED WHEN NOT INVOLVED IN PROT. SYNTHESIS • THEY ARE COMPOSED OF ABOUT 60% RNA (rRNA) AND 40% PROTEIN RIBOSOMAL SUBUNITS • THE SMALL AND LARGE SUBUNITS ARE: – CONSTRUCTED IN THE NUCLEOLUS – DISPATCHED THROUGH NUCLEAR PORES TO THE CYTOPLASM – ONCE IN CYTOPLASM, ARE ASSEMBLED INTO FUNCTIONAL RIBOSOMES ONLY WHEN ATTACHED TO AN mRNA RIBOSOMAL BINDING SITES • 1) mRNA BINDING SITE-CREATES COMPLEX • 2) P SITE - HOLDS THE tRNA CARRYING THE GROWING POLYPEPTIDE CHAIN • 3) A SITE - HOLD THE tRNA CARRYING THE NEXT A.A. TO BE ADDED • 4) E SITE - DISCHARGED tRNAs LEAVE THE RIBOSOME • ** AS THE RIBOSOME HOLDS THE tRNA AND mRNA MOLECULES TOGETHER, ENZYMES TRANSFER THE NEW A.A. FROM ITS tRNA TO THE CARBOXYL END OF THE GROWING POLYPEPTIDE ANATOMY OF A RIBOSOME BUILDING A POLYPEPTIDE • THE BUILDING OF A PROTEIN, OR TRANSLATION, OCCURS IN 3 STAGES: – 1)INITIATION – 2) ELONGATION – 3) TERMINATION ALL 3 STAGES REQUIRE ENZYMES AND OTHER PROTEIN FACTORS INITIATION AND ELONGATION REQUIRE ENERGY PROVIDED BY GTP INITIATION • INITATION BRINGS TOGETHER mRNA, A tRNA ATTACHED TO THE FIRST A.A.(METHIONINE), AND THE 2 RIBOSOMAL SUBUNITS • A) A SMALL RBIOSOMAL SUBUNIT BINDS TO A MOLECULE OF mRNA. AN INITIATOR tRNA, WITH ANTICODON UAC, BASE-PAIRS WITH START CODON AUG. THIS tRNA CARRIES METHIONINE • B) LARGE RIBOSOMAL SUBUNIT ARRIVES. THE INITIATOR tRNA IS IN THE P SITE. THE A SITE IS AVAILABLE FOR NEXT A.A. • GTP PROVIDES THE ENERGY FOR INITIATION INITIATION OF TRANSLATION ELONGATION • SEVERAL PROTEINS CALLED ELONGATION FACTORS TAKE PART IN THIS 3-STEP CYCLE, ADDING A.A’S • 1) CODON RECOGNITION: AN INCOMING AMINOACYL tRNA BINDS TO THE CODON IN THE A SITE – AN ELONGATION FACTOR DIRECTS tRNA INTO A SITE – HYDROLYSIS OF GTP PROVIDES ENERGY • 2) PEPTIDE BOND FORMATION: THE RIBOSOME CATALYZES THE FORMATION OF A PEPTIDE BOND BETWEEN THE NEW A.A. AND THE CARBOXYL END OF GROWING PROTEIN • 3) TRANSLOCATION- THE tRNA IN THE A SITE, WHICH IS NOT ATTACHED TO THE GROWING PEPTIDE, IS MOVED TO P SITE. THE tRNA THAT WAS IN THE P SITE IS TRANSLOCATED TO THE E SITE AND EXITS – THE mRNA IS MOVED THRU RIBOSOME IN THE 5’ TO 3’ DIRECTION – GTP HYDROLYSIS PROVIDES ENERGY ELONGATION TERMINATION • 1) WHEN RIBOSOME REACHES A TERMINATION CODON ON mRNA, THE A SITE ACCEPTS A PROTEIN CALLED A RELEASE FACTOR • 2) THE RELEASE FACTOR HYDROLYZES THE BOND BETWEEN THE tRNA IN THE P SITE AND THE LAST A.A. OF THE PEPTIDE CHAIN. IT IS FREED FROM THE RIBOSOME • 3) THE TWO RIBOSOMAL SUBUNITS AND THE OTHER COMPONENTS DISSOCIATE TERMINATION TRANSLATION VIDEO QuickTime™ and a Cine pak decomp ress or are nee ded to s ee this picture. SUMMARY OF PROTEIN SYNTHESIS POLYRIBOSOMES • A SINGLE RIBOSOME CAN MAKE AN AVERAGE SIZED PROTEIN IN LESS THAN A MINUTE, BUT CLUSTERS OF RIBOSOMES, CALLED POLYRIBOSOMES, CAN SIMULTANEOULSY TRANSLATE AN mRNA MOLECULE – ONCE A RIBOSOME PASSES THE INITIATION CODON, A SECOND RIBOSOME CAN ATTACH TO THE LEADER SEQUENCE OF mRNA – SEVERAL RIBOSOMES MAY TRANSLATE AN mRNA AT ONCE, MAKING MANY COPIES OF A POLYPEPTIDE POLYRIBOSOMES FROM POLYPEPTIDE TO FUNCTIONAL PROTEIN • THE BIOLOGICAL ACTIVITY OF PROTEINS DEPENDS UPON A PRECISE FOLDING OF THE POLYPEPTIDE CHAIN INTO A 3’D CONFORMATION – GENES DETERMINE PRIMARY STRUCTURE, THE LINEAR SEQUENCE OF AMINO ACIDS – PRIMARY STRUCTURE DETERMINES HOW THE POLYPEPTIDE CHAIN WILL SPONTANEOUSLY COIL AND FOLD TO FORM 3-D CONFORMATION POINT MUTATIONS • MUTATION = A CHANGE IN THE GENETIC MATERIAL OF A CELL • POINT MUTATION = A MUTATION LIMITED TO ABOUT ONE OR A FEW BASE PAIRS IN A SINGLE GENE. • THERE ARE 2 CATEGORIES OF POINT MUTATIONS: – 1) BASE-PAIR SUBSTITUTIONS – 2) BASE-PAIR INSERTIONS OR DELETIONS BASE-PAIR SUBSTITUTIONS • THIS IS THE REPLACEMENT OF ONE BASE PAIR WITH ANOTHER; OCCURS WHEN A NUCLEOTIDE AND ITS PARTNER IN THE COMPLEMENTARY DNA STRAND ARE REPLACED WITH ANOTHER PAIR OF NUCLEOTIDES – SOMETIMES HAS LITTLE IF ANY EFFECT – IT CAN SIGNIFICANTLY ALTER PROTEIN ACTIVITY – ON RARE OCCASIONS, CAN IMPROVE PROT. POINT MUTATIONS SICKLE CELL-CAUSED BY CHANGE IN BASE PAIR INSERTIONS OR DELETIONS • INSERTION - OF ONE OR MORE NUCLEOTIDE PAIRS INTO A GENE • DELETION - OF ONE OR MORE NUCLEOTIDE PAIRS INTO A GENE • MAY ALTER THE READING FRAME (TRIPLET GROUPING). THIS TYPE OF FRAMESHIFT MUTATION WILL OCCUR WHEN NUMBER OF NUCLEOTIDES INSERTED OR DELETED IS NOT A MULTIPLE OF 3 • THIS WILL PRODUCE A NONFUNCTIONAL PROTEIN UNLESS IT IS VERY NEAR END OF GENE MUTAGENS • MUTAGENESIS = THE CREATION OF MUTAGENS, WHICH CAN OCCUR AS ERRORS IN DNA REPLICATION, REPAIR, OR RECOMBINATIONS THAT RESULT IN BASE-PAIR SUBSTITUTIONS, INSERTIONS OR DELETION • MUTAGEN = PHYSICAL OR CHEMICAL AGENTS THAT INTERACT WITH GENETIC MATERIAL TO CAUSE MUTATIONS – RADIATION MOST COMMON PHYSICAL MUTATION