Involucrin is a key component of the cross-linked envelope of terminally
differentiated keratinocytes. The human molecule largely consists of 10 residue
repeats and forms a thin 460 A long rod. Summarized experimental data and a
detailed stereochemical analysis made with computer modeling resulted in a
structural model for the involucrin molecule. The suggested structure is a
left-handed alpha-helical solenoid built of a tandem array of helix-turn-helix
folds. The structure enables us to explain the whole set of experimental data
and residue conservations within the repeats. It is ideally suited to serve as a
scaffold for cell envelope assembly and proposes a possible mode of the
intermolecular interactions of involucrin during cell cornification.
Figure 1.
Fig. 1. Scheme of the repetitive multiplication of the 10
residue unit during search of the initial template for the
involucrin structure. α-Helical segments are represented by
cylinders. The crossing angle ω was used to vary the
orientation of the α-helical segments; Δz and Δφ are
components of the screw translation. Circles with ‘L’ on the
surface of the α-helices indicate location of leucines 5 and 8.
Figure 4.
Fig. 4. Diagram showing the solvent-accessible surface of a
fragment of the repetitive domain (residues 312–361) of human
involucrin. A dotted line winding around the involucrin groove
denotes a possible mode of peptide binding. For simplicity, only
C[β] atoms of the outside side chains are shown.
The above figures are
reprinted
by permission from the Federation of European Biochemical Societies:
FEBS Lett
(2000,
473,
127-131)
copyright 2000.
