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Protein Folding
Molecular Chaperones

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•Have protein, it is in primary structure
•Some proteins are incapable of folding correctly
•To fold correctly, they need molecular chaperones
•Things that help the proteins that are unbale to fold properly, help them to
•2 ways:
–Need atp
–One is Groel- threaded throiugh components to become active
–GroES
–DnaK
–DnaJ
–Need energy

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Protein Secretion
Signal Sequence

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   15to 20 amino acids.
   Located at beginning of protein.
   Signals cell’s secretory system that protein needs to be exported.
   Also prevents complete folding which will inhibit secretion.
   Necessary for proteins coming in and out of the cell

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SRP

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   small protein and 4.5S RNA.
   Recognizes signal sequence-containing protein and directs it to special membrane protein complex for secretion.
   In common diseases, where if protein doesn’t have these, protein wont be secreted or where supposed to go. Leads to diseases- ice hill

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Protein secretion

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Transported proteins are then threaded through the membrane in an unfolded state.

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Post-translational modification

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removal of signal sequence, during transport, by a protease.

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Secretion of Folded Proteins
TAT System

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   Some transported protein contain small cofactors.
   Added to protein as it is folded into its final form.
   These proteins are transported by the Twin Arginine Translocase protein export system.
   Signal sequence has a pair of arginines.
   These arginines are recognized by the TatBC proteins.

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Secretion of Folded Proteins
TAT System

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   TatBC proteins carry the protein (to be transported) to the TatA (membrane transporter).
   Energy for transport provided by proton motive force.
   Thus, proteins that function in energy metabolism are required in the periplasm.

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Mutation

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Inherited change in the nucleotide sequence of genome.
Beneficial, neutral, or detrimental.

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Mutation
Genotype

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nucleotide sequence of a trait.

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Mutation
Phenotype

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physical expression of the trait.

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Mutation
Wild-type

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is a strain isolated from nature.

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Mutation
Mutant

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is a strain carrying a change in nucleotide sequence.

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Genotype

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hisC gene-encodes histidine synthesis
(three lowercase followed by capital letter all in italics)

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Mutation
Phenotype

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   His+ or His- (capital letter followed by two lowercase letters with a + or -)
   His+ strain capable of making histidine.
   His- strain incapable of making histidine.

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Mutations

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•Change in nucleotide sequence
•Can occur spontaneously
•Are rare events approx. 10 to the minuse 9
•Are concern is anything that will increase mutation rate
•munigen- anything that will increase muation rate
•2 types= physical- xrys, ultraviolet light, gama rays, beta particles, radiation
•Chemical-

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Types of Mutations
Point mutations (bp substitution)

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single base pair substitution

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Types of Mutations
PKU

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individual has a one base pair change in gene for metabolims of phenylalanine

•Normal – when degrade phenylalanineà phenylpyruvic acid
•With PKU lack enzyme to break down properly
Convert phenylalanineà

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Types of point mutations
missence point mutation

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at instead of TA- faulty protein

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Types of Mutations
Nonsence mutation

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GC instead of CG- incomplete protein

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Types of Mutations
Silent mutation

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TA instead of CG- normal protein but is silent mutation= no effects.

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Types of Mutations
Frameshift mutations

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mutation, can have an insertion of an extra base pair or multiple base pairs or you can have deletion of single base pair or multiple base pair

•Reason called this is because, codons are shifted, frame is different. a no stop codon.
•Mostly detremental

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Types of Mutations
Frameshift mutations
Inversions

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piece chromosome taken out and then put back in after inverted

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Types of Mutations
Transposons

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insertion of a transposable element. If occurs within a gene, loss of gene function ocurrs. Jumping genes

•Able to cut themselves out of locas/location on the chromosome and move on another part of chromosome and insert themselve
•Can reinsert themselves on a different chromosome
•Loss gene function sometimes
•Rare and not found in every organism, movement is uncommon
•Barbra mcklintock discovered transposons in corn.

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Translocations

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•- in DNA its translocated somehwere else. Important if gene is supposed to be In certain place, what regulatest he gene will be lost.

•Cell making to much product

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Mutagenesis
Mutagens

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   agents that cause mutations.
Physical agents
   Radiation-Ionizing and non-ionizing radiation.
Chemical agents
   Nucleotide base analogs
   Alkylating agents
   Intercalating agents.

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Mutagenesis
Physical
Non-ionizing radiation-UV light sterilization

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   Useful for isolation of mutants
   Allows use to induce mutations and isolate mutants
   260 nm-wavelength of maximum absorption
   Formation of pyrimidine dimers-the covalent bonding together of adjacent pyrimidines (C or T).
   Causes a misread by DNA polymerase during replication

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Mutagenesis
Physical
Ionizing radiation-gamma, cosmic and X-rays.

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   Cause ionization of water and other substances which causes mutations.
   Free radicals react with and inactivate macromolecules such as DNA.à mutation or inactivation of DNA
   Superoxide, hydrogen peroxide
Repair mechanism
   Light repair and dark repair mechanisms

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Mutagenesis
Physical
DNA repair mechanisms

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enzyme systems that recognize damage to DNA, excise (cut out) the damaged base pairs, synthesize replacements, and insert correct bp sequence into DNA.
If damage to extensive, may not be bable to repair it

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Mutagenesis
Physical
Ames Test (Bruce Ames-Berkeley)

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   Determine mutagenesis and carcinogenesis of chemicals.
   Many chemicals don’t know what the mutagenesis is or carcinogenesis
   Cost a lot of money to stream chemicals and determine whether they are these.

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Mutagenesis
Ames Test

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Salmonella species that is His-.- lacked ability to make own histdadine amino acid
•Need to put histadine in the media

genetics – Microbiology – Flashcards

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