"The very idea that cells proofread their genetic information......One doesn't proofread gibberish. If
cells had cobbled together haphazard strings of building blocks, it wouldn't really matter in what order they were assembled. We know, of course, that the sequence matters: most mutations cause disease or death. Proofreading is evidence par excellence that genetic information represents real information, the kind found in books and software.
Cells inspect and correct their informational macromolecules at every stage: at transcription, at translation, and during post-translational modification. Roving molecular machines inspect other machines at work in the cell. They recognize misfolded proteins and tag them for degradation. And when the cell divides, molecular machines check every letter as DNA strands are duplicated. Cells are in the "quality control" business.
.....messenger RNA (mRNA) transcripts are read in sets of three letters (codons). Matching the mRNA codons are transfer RNA molecules (tRNA), each equipped with a matching "anticodon" at one end, and an amino acid at the other end (when fully loaded, they are called aminoacyl-tRNAs, or aa-tRNAs). As the codons and anticodons pair up in single file inside the ribosome, the amino acids fasten in single file with peptide bonds. The growing polypeptide chain will become a protein after translation is complete.
In short, proofreading needs to be energy efficient, but it won't happen without the expenditure of an energy-rich molecule to push it along. The reaction must favor getting the right molecule where it belongs.
Biochemists knew that each aa-tRNA has to be prepped for its role by binding to an assistant called Elongation Factor Tu (EF-Tu) plus a fuel molecule, GTP.
We have found that the bacterial ribosome uses two proofreading steps following initial selection of transfer RNAs (tRNAs) to maintain high accuracy of translation of the genetic code. This means that there are three selection steps for codon recognition by aa-tRNAs.
First, there is initial codon selection by aa-tRNA in ternary complex with elongation factor Tu (EF-Tu) and GTP.
Second, there is proofreading of aa-tRNA in ternary complex with EF-Tu and GDP.
Third, there is proofreading of aa-tRNA in an EF-Tu−independent manner, presumably after dissociation of EF-Tu·GDP from the ribosome....
This should cause even more grief for neo-Darwinism, because it shows that single-step proofreading "normally is remarkably high." In essence, the cell double-checks its already-accurate translation. They actually use the word "rechecking" to describe it. They estimate it provides a million-fold increase in accuracy,...
Engineers understand concepts like backups, redundancy, double-checking, and quality control. They realize that there are tradeoffs between accuracy and speed, so they seek to optimize competing design requirements." CEH
Thank you for making me so wonderfully complex!
Your workmanship is marvelous...
Psalm 139:14 NLT
Cells inspect and correct their informational macromolecules at every stage: at transcription, at translation, and during post-translational modification. Roving molecular machines inspect other machines at work in the cell. They recognize misfolded proteins and tag them for degradation. And when the cell divides, molecular machines check every letter as DNA strands are duplicated. Cells are in the "quality control" business.
.....messenger RNA (mRNA) transcripts are read in sets of three letters (codons). Matching the mRNA codons are transfer RNA molecules (tRNA), each equipped with a matching "anticodon" at one end, and an amino acid at the other end (when fully loaded, they are called aminoacyl-tRNAs, or aa-tRNAs). As the codons and anticodons pair up in single file inside the ribosome, the amino acids fasten in single file with peptide bonds. The growing polypeptide chain will become a protein after translation is complete.
In short, proofreading needs to be energy efficient, but it won't happen without the expenditure of an energy-rich molecule to push it along. The reaction must favor getting the right molecule where it belongs.
Biochemists knew that each aa-tRNA has to be prepped for its role by binding to an assistant called Elongation Factor Tu (EF-Tu) plus a fuel molecule, GTP.
We have found that the bacterial ribosome uses two proofreading steps following initial selection of transfer RNAs (tRNAs) to maintain high accuracy of translation of the genetic code. This means that there are three selection steps for codon recognition by aa-tRNAs.
First, there is initial codon selection by aa-tRNA in ternary complex with elongation factor Tu (EF-Tu) and GTP.
Second, there is proofreading of aa-tRNA in ternary complex with EF-Tu and GDP.
Third, there is proofreading of aa-tRNA in an EF-Tu−independent manner, presumably after dissociation of EF-Tu·GDP from the ribosome....
Engineers understand concepts like backups, redundancy, double-checking, and quality control. They realize that there are tradeoffs between accuracy and speed, so they seek to optimize competing design requirements." CEH
Thank you for making me so wonderfully complex!
Your workmanship is marvelous...
Psalm 139:14 NLT
