what are tautomeric compounds?
molecules that can exist in two or more interconvertable forms
differ in the position of a protein and a double bond
what are ß-turns?
loops which connect secondary structure elements
often at the protein surface, charged and hydrophilic
insertions and deletions betwen homologous proteins are often found in loops
bteween 2 beta sheets: ß-hairpin or ß-turn
how does a phoyphorylated histidine look like?
who has the most reactive side chain of all aa?
cysteine
very reactive -SH group
what does cysteine form easily?
disulfide bridges
what are acids and bases?
acid = proton donor
base = proton acceptor
what are the aromatic amino acids?
Phenylalanine, Tryptophan and Tyrosine
they all have a conjugated ring structure in their side chain, which allows them to absorb UV-light
what are RTKs?
receptor tyrosine kinases
the insulin receptor is one of the most famous and well studied examples
> is a covalent tetramer even before insulin binds
whats the FHA domain?
Fork Head associated domain
recognizes phosphotheorine residues on target proteins, distinguishing it from phosphoserine
what are the different protein structures?
amino acid sequence
locally regular structure such as alpha-helices and ßeta-strands
relative orientantion of secondary structure elements
spatial arrangement of multiple peptide chains
what are peptide bonds?
connection between aa
planar, rotation around this bond is restricted
two conformation: cis and trans
two backbone torsin angles:
N-Ca-bond = phi
Ca-CO-bonds= psi
what is cis and trans?
cis = substituent groups one the same side
trans: substituent groups on opposite sides
what are alpha-helices?
secondary structure elements
right handed
3.6 aa per turn
side chains orientated outwards
dipol moment - important for ligand bidning
whats the simplest and most common alpha-helical domain?
4-helix-bundle protein
helix axes are parallel to each other
hydrophobic side chain is in the core
often sequential helices with antiparallel orientation
how does alpha-helical proteins often occur?
as channels
helices are very hydrophobic
easy to predict
ion achnalles for K+, Na+,Ca2+
very selective
what are GPCRs?
G-protein coupled receptors
receptors in the membrane
signals for second messenger
7 transmembrane helices
largest family of integral membrane proteins
react to light, protein, peptides, small molecules, hormones and ions
whaat is the “greek motive”?
beta hairpin motif
four beta-neighboouring strands in antiparallel ß-sheets
what are characteristics of alpha/beta motifs?
C and N-termini far apart from each other when both strands are close
polypeptide chain must cross the sheet
connection oft contains an alpha-helix = ß-a-ß-motive
helix axes parallel with repects to the strands
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