Hydrophobic zipper model

The nucleation-condensation mechanism can be accommodated in modified framework and hydrophobic-collapse models the framework model must be modified so that formation of secondary structure is linked to the formation of tertiary interactions and the hydrophobic collapse model must have the formation of tertiary interactions linked to the formation of secondary structure. Another variation of concerted structure formation is the hydrophobic zipper. 68 Whatever the distinctions of names, stable tertiary and secondary structural interactions must form concurrently. 

The Leucine Zipper (LZ) is a dimerization motif found in the b-LZ and b-HLH-LZ ttanscription factor families (1,2). Upon dimerization, LZs fold into parallel and two-stranded a-helical coiled-coils (3-6). The primary structure of coiled-coils forming proteins is characterized by the heptad repeats (abcdefg)n where Leu residues are conserved at positions d and positions a are mostly occupied by P-branched and hydrophobic residues while e and g positions are often occupied by acidic or basic residues (7,8). The tertiary interactions of the dimeric LZ or parallel and two-stranded a-helical coiled-coils are described by the knobs-into-holes model (3,9). 

---