aa motif / Coiled-coils

3.6 a.a / turn in helix 

abcdefg 'a' &'d’ are hydrophobic residues 'e' and 'g' are found to be charged amino 

7.2 a.a / 2 turns acids 

 —7 amino acids per 2 turns in the helix 

For every turn there could be one hydrophobic residue coming same side of the helix 

Ex: GCN4

TLS Online TPP Program

#Id: 942

#Unit 5. Developmental Biology

Two major mechanisms during fertilization in sea urchin:

Species-specific sperm attraction 

Species-specific sperm activation

TLS Online TPP Program

#Id: 943

#Unit 5. Developmental Biology

Chemotaxis 

sperms are attracted toward eggs of their species by following a gradient of a chemical secreted by the egg.

TLS Online TPP Program

#Id: 944

#Unit 5. Developmental Biology

In Sea urchin,

Sperm-activating peptides provide direction to sperm during chemotaxis.

TLS Online TPP Program

#Id: 945

#Unit 5. Developmental Biology

SAP in the egg jelly of the sea urchin Arbacia punctulata 

Resact (14-amino acid chemotactic peptide)

TLS Online TPP Program

#Id: 946

#Unit 5. Developmental Biology

SAP in the egg jelly of, Strongylocentrotus purpuratus

Speract

TLS Online TPP Program

#Id: 947

#Unit 5. Developmental Biology

Resact from Arbacia egg jelly binds to its receptor on the sperm, activates the receptor’s guanylyl cyclase (RGC) activity.