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1

The fidelity of the translation of the genetic code

100%
Sankaranarayanan R.
Acta Biochimica Polonica
|
2001
|
tom 48
|
nr 2
Aminoacyl-tRNA syn the tas es play a cen tral role in main tain ing ac cu racy dur ing the trans la tion of the ge netic code. To achieve this chal leng ing task they have to dis crim i- nate against amino ac ids that are very closely re lated not only in struc ture but also in chem i cal na ture. A 'dou ble-sieve' ed it ing model was pro posed in the late sev en ties to ex plain how two closely re lated amino ac ids may be dis crim i nated. How ever, a clear un der stand ing of this mech a nism re quired struc tural in for ma tion on syn the tas es that are faced with such a prob lem of amino acid dis crim i na tion. The first struc tural ba sis for the editing model came recently from the crystal structure of isoleucyl-tRNA synthetase, a class I synthetase, which has to dis crim i nate against valine. The struc­ture showed the pres ence of two cat a lytic sites in the same en zyme, one for ac ti va tion, a coarse sieve which binds both isoleucine and valine, and an other for ed it ing, a fine sieve which binds only valine and rejects isoleucine. An other struc ture of the en zyme in com plex with tRNA showed that the tRNA is re spon si ble for the translocation of the misactivated amino-acid substrate from the catalytic site to the editing site. These studies were mainly fo cused on class I syn the tas es and the sit u a tion was not clear about how class II enzymes discriminate against similar amino acids. The recent struc tural and en zy matic stud ies on threonyl-tRNA synthetase, a class II en zyme, re­veal how this chal leng ing task is achieved by us ing a unique zinc ion in the ac tive site as well as by em ploy ing a sep a rate do main for spe cific ed it ing ac tiv ity. These stud ies led us to pro pose a model which em pha sizes the mir ror sym met ri cal ap proach of the two classes of en zymes and high lights that tRNA is the key player in the evo lu tion of these class of enzymes.
2

From accuracy in protein synthesis to cardiovascular disease: The role of homocysteine

86%
Jakubowski H.
Biotechnologia
|
2002
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nr 3
3
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On the border between biology, mathematics and computer science

58%
Formanowicz P.
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
|
2011
|
tom 92
|
nr 3
4

The new aspects of aminoacyl-tRNA synthetases

58%
Szymanski M., Deniziak M., Barciszewski J.
Acta Biochimica Polonica
|
2000
|
tom 47
|
nr 3
Aminoacyl-tRNA synthetases (AARS) are essential proteins found in all living organisms. They form a diverse group of enzymes that ensure the fidelity of transfer of genetic information from the DNA into the protein. AARS catalyse the attachment of amino acids to transfer RNAs and thereby establish the rules of the genetic code by virtue of matching the nucleotide triplet of the anticodon with its cognate amino acid. Here we summarise the effects of recent studies on this interesting family of multifunctional enzymes.
5
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Two approaches to the description of distribution keys in crop simulation models

58%
Poluektov R. A., Zakharova E. T.
International Agrophysics
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2000
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tom 14
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nr 1
6

The genetic code - 40 years on

58%
Szymanski M., Barciszewski J.
Acta Biochimica Polonica
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2007
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tom 54
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nr 1
The genetic code discovered 40 years ago, consists of 64 triplets (codons) of nucleotides. The genetic code is almost universal. The same codons are assigned to the same amino acids and to the same START and STOP signals in the vast majority of genes in animals, plants, and microorganisms. Each codon encodes for one of the 20 amino acids used in the synthesis of proteins. That produces some redundancy in the code and most of the amino acids being encoded by more than one codon. The two cases have been found where selenocysteine or pyrrolysine, that are not one of the standard 20 is inserted by a tRNA into the growing polypeptide.
7

Synthesis, physicochemical and biological properties of poly-alpha-amino acids - the simplest of protein models

58%
Katchalski-Katzir E.
Acta Biochimica Polonica
|
1996
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tom 43
|
nr 1
During the 1950s, linear and multichain poly-a-amino acids were synthesized by polymerization of the corresponding N-carboxy-amino acid anhydrides in solution in the presence of suitable catalysts. The resulting homo- and heteropolymers have since been widely employed as simple protein models. Under appropriate conditions, poly-a-amino acids, in the solid state and in solution, were found to acquire conformations of an a-helix and of (^-parallel and antiparallel pleated sheets, or to exist as random coils. Their use in experimental and theoretical investigations of helix-coil transitions helped to shed new light on the mechanisms involved in protein denaturation. Poly-a-amino acids played an important role in the deciphering of the genetic code. In addition, analysis of the antigenicity of poly-a-amino acids led to the elucidation of the factors determining the antigenicity of proteins and peptides. Interest in the biological and physicochemical characteristics of poly-a-amino acids was recently renewed because of the reported novel findings that some copolymers of amino acids are effective as drugs in multiple sclerosis, and that glutamine repeats and reiteration of other amino acids occur in inherited neurodegenerative diseases. The presence of repeating sequences of amino acids in proteins, and of nucleotides in DNA, raises many interesting questions about their respective roles in determining protein structure and function, and gene performance and regulation.
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