Conformation of a clathrin triskelion in solution

Area of Science:

• Cell Biology
• Biophysics
• Structural Biology

Background:

• Clathrin is a key protein in vesicle formation, assembling into polyhedral cages.
• Clathrin forms a three-legged heteropolymer called a triskelion.
• In vitro, clathrin cage assembly is pH-dependent, favoring lower pH.

Purpose of the Study:

• To determine the structural parameters of isolated clathrin triskelia.
• To investigate triskelion conformation during cage assembly.
• To correlate solution measurements with structural data from cryo-electron microscopy.

Main Methods:

• Static and dynamic light scattering techniques were employed.
• Measurements determined the radius of gyration (R(g)) and hydrodynamic radius (R(H)).
• Rigid molecular bead models were used for calculations.

Main Results:

• Measured R(g) and R(H) values for isolated triskelia were obtained under conditions favoring cage assembly.
• Calculations indicated that leg bending and vertex puckering account for the measured radii.
• Solution conformation of triskelia aligns with cryo-EM data of clathrin cages.

Conclusions:

• The study characterizes the solution structure of clathrin triskelia.
• Conformational flexibility, including leg bending and vertex puckering, is crucial for triskelion structure.
• Findings support the structural model of clathrin cage formation and are consistent with cryo-EM observations.