Proline codons

C. UCA is a codon for serine. It is converted to a termination codon by mutation A, to a proline codon by mutation B, to a threonine codon by mutation D, and to an alanine codon by mutation E. Only mutation C would produce no change in the protein, since UCU is also a codon for serine. 

Tabk I shows the rq)lacement of amino add residues by nonsynonymous nucleotide substitutions in the S conserved amino add sequences on the ALS enzyme. The alteration of tyrosine (Y) to histidine (H) in the first amino acid sequence (1) of R on A was found in 1 resistant bio pe. But it seems tiiat this replacement does not confer resistance, because the other resistant biotypes did not have such a replacement All S resistant biotypes had various point mutations (A, S, L) in the codon for a proline residue (P) in the second amino acid sequence (2) of Region A, whereas all 7 susceptible biotypes had the proline residue (P). Because this proline codon (P) is common with oth susceptible plants sequenced so far, it is possible tiiat its replacement confers resistance to SU herbicides in L, micrantha. Finalty, all of the resistant plants had an alteration from proline (P) to s me (A), alanine (S), or lysine (L) compared with the amino acid sequence of susceptible plants reported. 

The many (possibly more than 30) types of collagens found in human connective tissues have substantially the same chemical structure consisting mainly of glycine with smaller amounts of proline and some lysine and alanine. In addition, there are two unusual amino acids, hydroxyproline and hydroxylysine, neither of which has a corresponding base-triplet or codon within the genetic code. There is therefore, extensive post-translational modification of the protein by hydroxylation and also by glycosylation reactions. 

Missense mutation The codon containing the changed base may code for a different amino acid. For example, if the serine codon UCA is given a different first base—C—to become CCA, it will code for a different amino acid, in this case, proline. This substitution of an incorrect amino acid is called a "missense" mutation. 

Hydroxyproline is formed by a posttranslational modification of proline residues in the protein. The 14C-labeled hydroxyproline is not incorporated directly into the collagen because there is no genetic codon to specify the incorporation of hydroxyproline. 

Table 6.1 shows the relationship between the codon sequence in mRNA and its corresponding amino acid in the new protein. Because there are 64 (43) different anticodon combinations and only 20 encoded amino acids, some different anticodon sequences encode for the same amino acid. Generally, all the anticodons matching a given amino acid will have the same first two nucleotides. Exceptions are arginine, serine, and isoleucine. For example, the codon for proline will always start with CC, but the arginine codon may start with either AG or CG. The 3 end of the tRNA anticodon pairs with the 5 end of the mRNA codon. In other words, the codon and anticodon align and bind in an antiparallel fashion. 

Selective formation of microparticles from polynucleotides and lysine-rich proteinoids rich in individual radioactive amino acid has been studied and the focus of attention is on those homoanticodonic amino acids having one homogeneous codon (glycine, CCC lysine, UUU proline, GGG and phenylalanine, AAA)58). Precipitation of individual amino acid rich proteinoids with each of homopolyribonucleotides, with and without Mg2+, was tested58>. The results show that three (Lys-rich, Gly-rich,... 

Masugi, J., Tamori, Y., Mori, H., Koike, T., and Kasuga, M. (2000). Inhibitory effect of a Proline- to-Alanine Substitution at Codon 12 of Peroxisome Proliferator Activated Receptor y2 on Thiazolidinedione-Induced Adipogenesis. Biochem. Biophys. Res. Commun. 268, 178—182. 

The tRNA for proline, which has the anticodon GGG, hydrogen bonds to the CCC codon for proline in the mRNA and brings its attached proline amino acid into position for attachment to the growing protein chain. Then the tRNA for phenylalanine hydrogen bonds to the codon for phenylalanine in the mRNA and brings its attached phenylalanine into position for attachment to the proline. This process continues until a stop signal is reached. 

Hydroxyproline is a very unusual amino acid. There is no genetic codon for the insertion of Hyp into a growing protein because collagen is not made that way. The collagen molecule is first assembled with Pro where Hyp ends up. Then some proline residues are oxidized to... 

The mouse Dtnbpl transcript identified as a on AceView is predicted to encode a protein of 408 aa, which is 56 aa longer than the largest mouse dysbindin-1A isoform reported in the literature (i.e., the 352 aa isoform of Benson et al., 2001). If we accept the first ATG in transcript a as the start codon, the predicted protein matches the 352 aa isoform. AceView instead lists the longer possibility for two reasons. Near the 5 end of the transcript is a less common start codon sequence (CTG). Between the 5 end and the first ATG sequence are 168 nucleotides potentially encoding an arginine-proline rich N-terminal extension that may serve as a nuclear localization signal of functional interest. Indeed, the 408 aa variant of dysbindin-1 A has been predicted in mouse undifferentiated limb mesenchyme (NCBI accession no. AAH48682). But it is not predicted elsewhere. In most tissues, then, transcript a is probably translated as the 352 aa isoform. 

The genes for all three deiodinases contain the TGA triplet in the coding region of the DNA, while the mRNA contains a UGA triplet at the corresponding position. Part of the coding sequence of type II deiodinase is shown in what follows. The entire protein consists of 266 amino acids. The codon resulting in selenocysteine is indicated by "SeC," where this amino acids resides in the context -glycine-serine-alanine-threonine-selenocysteine-proline-proline-phenylalanine-threonine- (Pallud et al., 1997) ... 

The DNA sequence M, shown below, is the sense strand from a coding region known to be a mutational hot spot for a gene. It encodes amino acids 21 to 25. Given the genetic and amino acid codes CCC = proline (P), GCC = alanine (A), TTC = phenylalanine (F), and TAG = stop codon, which of the following sequences is a frame-shift mutation that causes termination of the encoded protein ... 

It follows that the array of codons represents the instructions for producing 20 amino acids, the so-called common amino acids. These amino acids are named and symbolized as alanine (Ala), arginine (Arg), asparagine (Asn), aspartate (Asp), cysteine (Cys), glutamine (Gin), glutamate (Glu), glycine (Gly), histamine (His), isoleucine (lie), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr), and valine (Val). 

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