高等教学大一英语下课件:ProteinStructureandFunction.ppt
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- 高等 教学 大一 英语 下课 ProteinStructureandFunction
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1、12(I)Secondary Structure:The local spatial arrangement of amino acid residues that are nearby in the sequence,that is,the relative positions of backbone atoms of a certain peptide segment.The side chains are not considered.Forms:helix,pleated sheet,turn,helix,random coil Major Bond:Hydrogen bond I.C
2、onformation of Protein3Right-handed helix3.6 amino acid residues per turn of helixThe pitch of the helix is 0.54nm,diameter is 0.23nmThe N-H of every peptide bond is hydrogen-bonded to the C=O of neighboring peptide bond located four peptide bonds away in the same chain.,including 13 atoms,so also k
3、nown as 3.613 helix.All the main chain C=O and NH are hydrogen bonded.Linus Pauling 1.-helix(1)4The alpha helix is a coiled secondary structure due to a hydrogen bond every fourth amino acid56Direction of hydrogen bonds are parallel to the vertical axis of helix.The stability of an-helix arises prim
4、arily from hydrogen bonds.The side chains are on the outside of the helix,not directly participate in the formation of helix.-helix is the most stable secondary conformation1.-helix(2):78Adjacent peptide unit form a zigzag or pleated pattern,the intersection angle is 110。.-Sheets are stabilized by h
5、ydrogen bonding between polypeptide strands.The direction of hydrogen bonds are vertical to the peptide strands.Adjacent chains in a b sheet can run in opposite directions(antiparallel b sheet)or in the same direction(parallel b sheet).The side chains of adjacent amino acids point in opposite direct
6、ions2.-pleated sheet structure 91011Peptide chain arises a tight 180turn.A-turn involves four amino acid residues,the first residues is hydrogen bonded to the fourth.Proline is often present in-turnOften lie on the globulin surface and serve key biologic role.3.-turn1213Left-handed helix,4.4 amino a
7、cid residues per turn.Hydrogen bonds stabilize the-helix,every hydrogen bond across 18 atoms,so also named as 4.418 helix.Often found in collagen.Triple left-handed helixes twist to form right-handed super helix and turn to collagenous fibers.4.-helix1415uGeneral name of a series of unordered confor
8、mation in protein.u Important structural and functional segments of protein.5.Random Coil166.Supersecondary Structure of Cytochrome C of PCNAof plasminogen17Motif in Calcium-binding Protein Zinc Finger Side chains can disrupt or induce the formation of secondary structure Shape:Pro having a rigid ri
9、ng(helix disrupter)Size:helix and -sheet needs AAs of small side chain.Leu,Ile,Trp,and Asn,having bulky sides,hard to form helix and-sheet)Charge:Too many charged AAs in a short region of one peptide is hard to form helix.1819*Definition:The entire three-dimensional conformation of a polypeptide cha
10、in.It refers to the spatial arrangement of amino acid residues that are far apart in the sequence and to the pattern of disulfide bonds.It indicates,in three-dimensional space,how secondary structural assemble to form domains and how these domains relate spatially to one another.(II)Tertiary Structu
11、re 20uSingle or several super secondary structure units gather and fold independently into a compact,stable structure,termed domain.uDomain is the function element of protein.The different domains of a protein are often associated with different functions.uDomain is the partial folding region at the
12、 level of tertiary structure.Motif is its subunit.uEvery domain is encoded by one exon.Domain(结构域(结构域)21NADHPyruvateLactate Dehydrogenase N terminalC terminal EGF ReceptorIntracellular protein kinase domain is regulated via the binding of the peptide hormone EGF to its extracellular domain.2223*Feat
13、ures:To the single peptide protein,tertiary structure is the highest level of structure.Form hydrophilic surface and hydrophobic inner core.*Major Bond:Hydrophobic Interaction24Myoglobin(肌红蛋白肌红蛋白)25Quaternary structure defines the polypeptide composition of a protein for an oligomeric protein,and th
14、e spatial relationships between its subunits.Subunit(亚基(亚基)Each polypeptide chain in such a protein is called a subunit.Subunit is inactive when it exists alone.(III)Quaternary Structure 26Features:l Quarternary structure arises when two or more polypeptides join to form a proteinl Subunit is inacti
15、ve when it exists on its own.l Subunits are linked by secondary bonds(H-bonds,ionic interactions,and hydrophobic interactions)l If the peptide chains are linked by covalent bonds(disulfide bond),it is not belong to quaternary structure.l Polypeptide chains can be in dimer,trimer.,as well as homo-or
16、hetero-form.For example,hemoglobin is composed of 4 polypeptide chainsLink to video27NH3 COO 2 NH3 COO 2 COO NH3 1COO NH3 1Asp HisArg Asp LysLys Asp ArgHis Asp94 146141 126 4040 126 141146 94Ionic Forces in Hemoglobin282930 Primary Structure:Peptide bond、Disulfide bond Secondary Structure:Hydrogen b
17、ond Tertiary Structure:Hydrophobic interaction Quaternary Structure:Ioni c bond (IV)Non-covalent Bonds stabilize Protein Structure31 Hydrogen bondA hydrogen atom is shared by two other atoms.H-donor:the atom to which H atom is more tightly attached,and the other is H-acceptor.32 Hydrophobic interact
18、ionNonpolar molecules tend to cluster together in water,that is,amino acids with nonpolar side chains cluster in the core of the protein,out of contact with water33 A charged group is able to attract another group of opposite charges.Ionic interaction34 The attraction between a pair of atoms increas
19、es as they come closer,until they are repelled by van der Waals contact distance.van der Waals force 35 Disulfide bridgeStrong covalent bonds between sulfur atoms in the amino acid cysteine36The folding of many proteins is protected by chaperonin proteins that shield out bad influences.Chaperon37Pos
20、t-translational Modification3839II.Structure-Function Relationship of Proteins Sequence of DNA Amino acid sequence of proteinConformation of ProteinFunction of ProteinPrimary structure is basis,Conformation is the key factor.401.The alternation of key AAs in a protein will cause the loss of its biol
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