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One of the cell populations is fed with growth medium containing normal amino acids. In contrast, the second population is fed with growth medium containing amino acids labeled with stable (non-radioactive) heavy isotopes. For example, the medium can contain arginine labeled with six carbon-13 atoms (13 C) instead of the normal carbon-12 (12 C ...
There are two protein products of the KRAS gene in mammalian cells that result from the use of alternative exon 4 (exon 4A and 4B respectively): K-Ras4A and K-Ras4B. These proteins have different structures in their C-terminal region and use different mechanisms to localize to cellular membranes, including the plasma membrane. [8]
The abundance of 15 N in some amino acids reflects an organism's position in a food web. This is due to the ways organisms metabolize different amino acids when they are consumed. Trophic amino acids (TrAAs) are first deaminated, meaning that the amino group is removed to produce an alpha-keto acid carbon skeleton.
One end of the chains (with a double stranded structure in which the 5' and 3' ends are adjacent to each other), the amino acids acceptor stem, usually attaches to amino acids and such reactions are often catalyzed by a specific enzymes, aminoacyl tRNA synthetase. [3]
Amino acids with the structure NH + 3 −CXY−CXY−CO − 2, such as β-alanine, a component of carnosine and a few other peptides, are β-amino acids. Ones with the structure NH + 3 −CXY−CXY−CXY−CO − 2 are γ-amino acids, and so on, where X and Y are two substituents (one of which is normally H). [7]
The primary structure of a biopolymer is the exact specification of its atomic composition and the chemical bonds connecting those atoms (including stereochemistry).For a typical unbranched, un-crosslinked biopolymer (such as a molecule of a typical intracellular protein, or of DNA or RNA), the primary structure is equivalent to specifying the sequence of its monomeric subunits, such as amino ...
The synthetase first binds ATP and the corresponding amino acid (or its precursor) to form an aminoacyl-adenylate, releasing inorganic pyrophosphate (PPi).The adenylate-aaRS complex then binds the appropriate tRNA molecule's D arm, and the amino acid is transferred from the aa-AMP to either the 2'- or the 3'-OH of the last tRNA nucleotide (A76) at the 3'-end.
The spiral has about 3.6 amino acids per turn, and the amino acid side chains stick out from the cylinder of the helix. Beta pleated sheets are formed by backbone hydrogen bonds between individual beta strands each of which is in an "extended", or fully stretched-out, conformation.