2.3.4 The planes of the peptide bonds arrange as pleated sheets. 2.3.5 Ther groups of adiacent residues protrude in opposite directions. 2.3.6 The adiacent polypeptide chains can be either parallel (the same direction) or antiparallel(the opposite direction)
2.3.4 The planes of the peptide bonds arrange as pleated sheets. 2.3.5 The R groups of adjacent residues protrude in opposite directions. 2.3.6 The adjacent polypeptide chains can be either parallel (the same direction) or antiparallel (the opposite direction)
(a) Antiparallel Top view Side view
(b)Parallel Top view Q Side view
3. Protein architecture can be understood at different levels 3.1 Each protein usually has one native conformation 3.1.1 Under physiological conditions of solvent and temperature, each protein folds spontaneously into one three-dimensional conformation. called the native conformation 3.1.2 This conformation is usually thermodynamically the most stable(having the lowest Gibb's free energy), and predominates among the innumerable theoretically possible ones. 3.1.3 Usually only the native conformation is functional
3. Protein architecture can be understood at different levels. 3.1 Each protein usually has one native conformation 3.1.1 Under physiological conditions of solvent and temperature, each protein folds spontaneously into one three-dimensional conformation, called the native conformation. 3.1.2 This conformation is usually thermodynamically the most stable (having the lowest Gibb’s free energy), and predominates among the innumerable theoretically possible ones. 3.1.3 Usually only the native conformation is functional
3.2 Protein structures have conventionally been considered at four different levels 3.2.1 The primary structure is the amino acid sequence (including the locations of disulfide bonds). 3.2.2 The secondary structure refers to the regular recurring arrangements of adjacent residues resulting mainly from hydrogen bonding between backbone groups, with a-helices and b-pleated sheets being the two most common ones 3.2.3 The tertiary structure refers to the spatial relationship among all amino acid residues in a polypeptide chain, that is, the complete three dimensional structure 3.2.4 The quaternary structure refers to the spatial arrangements of each subunit in a multisubunit protein, including nature of their contact
3.2 Protein structures have conventionally been considered at four different levels. 3.2.1 The primary structure is the amino acid sequence (including the locations of disulfide bonds). 3.2.2 The secondary structure refers to the regular, recurring arrangements of adjacent residues resulting mainly from hydrogen bonding between backbone groups, with a-helices and b-pleated sheets being the two most common ones. 3.2.3 The tertiary structure refers to the spatial relationship among all amino acid residues in a polypeptide chain, that is, the complete threedimensional structure. 3.2.4 The quaternary structure refers to the spatial arrangements of each subunit in a multisubunit protein, including nature of their contact