讲义第4讲 蛋白质结构基础-2

1、5.5 三级结构与折叠模式5.6 球蛋白的特征及性质5.7 蛋白质相互作用5.4 蛋白质二级结构与超二级结构由2-3个基本二级结构（、）组成的模体(motif例：4螺旋束、发夹结构等 -hairpins are one of the simplest super-secondary structures and are widespread in globular proteins. The 1st residue in Type I adopts the left-handed -helical conformation and therefore shows preference forg

2、lycine, asparagine or aspartate Anti -parallel -strands forming a -hairpin can accommodate a 90 degree change in direction known as a -corner The loop regions connecting -helical segments 例：cro repressor from phage lambda例：EF hand parallel -strands are connected by longer regions of chain which cros

3、s the -sheet and frequently contain -helical segments. This motif is called the -a-motif-a-motif is found in most proteins that have a parallel -sheetThe helix axis is roughly parallel with the -strands and all three elements of secondary structure interact forming a hydrophobic core 多肽链折叠，以某种特定形式将二

4、级结构元件组装起来象、是二级结构的单元一样，结构域是三级结构的单元在多结构域的蛋白质中，三级结构还包括结构域的组装三级结构的分类：型、型、/型、+型、无规型1. 小蛋白含单个螺旋例alamethicin, a transmembranevoltage gated ion channel, acting as a peptide antibiotic.2. The helix-turn-helix motif ：例RNA-binding protein Rop, found in certain plasmids(small circular molecules of double-strand

5、ed DNA occurring in bacteria and yeast and involved in their replication. There is a slight twist in the arrangement as shown3. The four-helix bundle 例:cytochrome c' 例:ferritin 4. domains which bind DNAengrailed homeodomain binding to DNAcro repressor from phage 4345. Globins6. Helix-helix packi

6、ng 7. Other distinctive all-a proteinsAnnexin V Parvalbumin-like calcium-binding proteins1. b sandwiches & barrelsAligned and orthogonal b sandwichesOrthogonal sheet packingsconsist of sheets folded on themselves; the two sheets make an angle of -90° Diagram of this -sheet arrangement in th

7、eLipocalin family, which bind small molecules between the sheets of thesandwic barrels: Some antiparallel-sheet2. Up-and -down antiparallel b sheetsThree up-and-down -strands connected by hairpins are followed by a longer connection to the fourth strand, which lies adjacent to the first jellyroll fo

8、ld as being formed by the addition of an extra "swirl" to a Greek key3. b -propellors : One molecule is composed of four : of these subunits. Each is a superbarrel of sixfour-stranded antiparallelsheets. The whole structure has a basically up-down topology and is called a b-propellor .4 b-

9、trefoils: This fold has an approximately 3-fold axis of symmetry.5 b-Helix: The b-strands wind round the structure describing a helical topologyRepeating b-a-bsupersecondary units, such that the outer layer of the structure is composed of ahelices packing against a central core of parallel b-sheets.

10、 These folds are called a/b, or wound abMany enzymes, including all those involved in glycolysis , are a/bstructures. Most a/bproteins are cytosolicThe -is always right-handedRossman FoldPlacental ribonucleaseinhibitor:17-stranded parallel sheet curved into an open horseshoe shape, with 16 -helices packed against the outer surfaceIf the first strand hydrogen bonds to the last, then the structure closes on itself forming a barrel-like structure Triose phosphatefolds which include significant alpha and beta