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The peptide backbone dihedral angles (φ, ψ) are about (–140°, 135°) in antiparallel sheets. In this case, if two atoms C α i and C α j are adjacent in two hydrogen-bonded β-strands, then they form two mutual backbone hydrogen bonds to each other's flanking peptide groups; this is known as a close pair of hydrogen bonds.
Peptide bond formation via dehydration reaction. When two amino acids form a dipeptide through a peptide bond, [1] it is a type of condensation reaction. [2] In this kind of condensation, two amino acids approach each other, with the non-side chain (C1) carboxylic acid moiety of one coming near the non-side chain (N2) amino moiety of the other.
However, additional molecular interactions may render the amide form less stable; the amino group is expelled instead, resulting in an ester (Ser/Thr) or thioester (Cys) bond in place of the peptide bond. This chemical reaction is called an N-O acyl shift. The ester/thioester bond can be resolved in several ways:
[1] [2] [3] The hydrogen bonding pattern in an alpha sheet is similar to that of a beta sheet, but the orientation of the carbonyl and amino groups in the peptide bond units is distinctive; in a single strand, all the carbonyl groups are oriented in the same direction on one side of the pleat, and all the amino groups are oriented in the same ...
The peptidyl transferase center (EC 2.3.2.12) is an aminoacyltransferase ribozyme (RNA enzyme) located in the large subunit of the ribosome.It forms peptide bonds between adjacent amino acids during the translation process of protein biosynthesis. [1]
According to one definition, a turn is a structural motif where the C α atoms of two residues separated by a few (usually 1 to 5) peptide bonds are close (less than 7 Å [0.70 nm]). [1] The proximity of the terminal C α atoms often correlates with formation of an inter main chain hydrogen bond between the corresponding residues. Such hydrogen ...
Prior to peptide bond formation, an aminoacyl-tRNA is bound in the A-site, a peptidyl-tRNA is bound in the P-site, and a deacylated tRNA (ready to exit from the ribosome) is bound to the E-site. Translation moves the tRNA from the A-site through the P- and E-sites, with the exception of the initiator tRNA, which binds directly to the P-site. [9]
The ω angle at the peptide bond is normally 180°, since the partial-double-bond character keeps the peptide bond planar. [3] The figure in the top right shows the allowed φ,ψ backbone conformational regions from the Ramachandran et al. 1963 and 1968 hard-sphere calculations: full radius in solid outline, reduced radius in dashed, and ...