Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genetic code”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1965

The genetic code.

Explore the source record for details and available documents.

Genetic Code↗
PubMed1995

Specific aminoacylation of C4N hairpin RNAs with the cognate aminoacyl-adenylates in the presence of a dipeptide: origin of the genetic code.

A series of C4N hairpin RNAs bearing anticodon nucleotides at the 5' ends and a discriminator base and the sequence CCA at the 3' ends was constructed by an in vitro transcription system using T7 RNA polymerase. These RNAs were aminoacylated specifically with their cognate amino acids by reaction with aminoacyl-adenylates in the presence of a dipeptide, valyl-aspartic acid, suggesting that such hairpin RNAs are able to play the role of the present-day tRNA and that valyl-aspartic acid can perform the function of the present-day aminoacyl-tRNA synthetase as a catalyst in the aminoacylation reaction. These results should provide a useful clue to elucidating the origin of the genetic code.

Adenosine Monophosphate↗
PubMed2001

Analysis of codon:anticodon interactions within the ribosome provides new insights into codon reading and the genetic code structure.

Although the decoding rules have been largely elucidated, the physical-chemical reasons for the "correctness" of codon:anticodon duplexes have never been clear. In this work, on the basis of the available data, we propose that the correct codon:anticodon duplexes are those whose formation and interaction with the ribosomal decoding center are not accompanied by uncompensated losses of hydrogen and ionic bonds. Other factors such as proofreading, base-base stacking and aminoacyl-tRNA concentration contribute to the efficiency and accuracy of aminoacyl-tRNA selection, and certainly these factors are important; but we suggest that analyses of hydrogen and ionic bonding alone provides a robust first-order approximation of decoding accuracy. Thus our model can simplify predictions about decoding accuracy and error. The model can be refined with data, but is already powerful enough to explain all of the available data on decoding accuracy. Here we predict which duplexes should be considered correct, which duplexes are responsible for virtually all misreading, and we suggest an evolutionary scheme that gave rise to the mixed boxes of the genetic code.

Anticodon↗
PubMed2005

RNA affinity for molecular L-histidine; genetic code origins.

Selection for affinity for free histidine yields a single RNA aptamer, which was isolated 54 times independently. This RNA is highly specific for the side chain and binds protonated L-histidine with 10(2)-10(3)-fold stereoselectivity and a dissociation constant (K(D)) of 8-54 microM in different isolates. These histidine-binding RNAs have a common internal loop-hairpin loop structure, based on a conserved RAAGUGGGKKN(0-36) AUGUN(0-2)AGKAACAG sequence. Notably, the repetitively isolated sequence contains two histidine anticodons, both implicated by conservation and chemical data in amino acid affinity. This site is probably the simplest structure that can meet our histidine affinity selection, which strengthens experimental support for a "stereochemical" origin of the genetic code.

Amino Acids↗
PubMed1985

A multivariate study of the relationship between the genetic code and the physical-chemical properties of amino acids.

The 20 naturally occurring amino acids are characterized by 20 variables: pKNH2, pKCOOH, pI, molecular weight, substituent van der Waals volume, seven 1H and 13C nuclear magnetic resonance shift variables, and eight hydrophobicity-hydrophilicity scales. The 20-dimensional data set is reduced to a few new dimensions by principal components analysis. The three first principal components reveal relationships between the properties of the amino acids and the genetic code. Thus the amino acids coded for by adenosine (A), uracil (U), or cytosine (C) in their second codon position (corresponding to U, A, or G in the second anticodon position) are grouped in these components. No grouping was detected for the amino acids coded for by guanine (G) in the second codon position (corresponding to C in the second anticodon position). The results show that a relationship exists between the physical-chemical properties of the amino acids and which of the A (U), U (A), or C (G) nucleotide is used in the second codon (anticodon) position. The amino acids coded for by G (C) in the second codon (anticodon) position do not participate in this relationship.

Amino Acids↗
PubMed1987

Hydrogen bonding between cytosine and peptides of threonine or serine: is it relevant to the origin of the genetic code?

13C, 15N, and 1H nuclear magnetic resonance measurements indicate that chloroform-soluble threonine-containing tripeptide derivatives, such as t-Boc-Thr-Gly-Gly-OBz, form three strong hydrogen bonds to the cytosine moiety of 2',3'-O-isopropylidene-5'-O-t-butyldimethylsilylcytidine. The C = O and NH of the central peptide residue plus the OH of the threonine side chain appear to form bonds to the N(4')H2, N(3), and C(2) = O, respectively, of the pyrimidine. An association constant calculated from the cytidine 15N(4') nuclear magnetic resonance response to added peptide is four times larger than the corresponding cytosine-guanine constant. It is suggested that cytosine-peptide bonding was part of the primitive genetic coding mechanism early in evolution and accounts for the origin of the cytosine-centered codons for the hydroxy amino acids, serine and threonine, in the present code.

Codon↗
PubMed2004

Expanding the genetic code.

Although chemists can synthesize virtually any small organic molecule, our ability to rationally manipulate the structures of proteins is quite limited, despite their involvement in virtually every life process. For most proteins, modifications are largely restricted to substitutions among the common 20 amino acids. Herein we describe recent advances that make it possible to add new building blocks to the genetic codes of both prokaryotic and eukaryotic organisms. Over 30 novel amino acids have been genetically encoded in response to unique triplet and quadruplet codons including fluorescent, photoreactive, and redox-active amino acids, glycosylated amino acids, and amino acids with keto, azido, acetylenic, and heavy-atom-containing side chains. By removing the limitations imposed by the existing 20 amino acid code, it should be possible to generate proteins and perhaps entire organisms with new or enhanced properties.

Amino Acids↗