The papillomavirus major late protein, L1, forms the pentameric assembly un
it of the viral shell. Recombinant HPV16 L1 pentamers assemble in vitro int
o capsid-like structures, and truncation of ten N-terminal residues leads t
o a homogeneous preparation of 12-pentamer, icosahedral particles. X-ray cr
ystallographic analysis of these particles at 3.5 Angstrom resolution shows
that L1 closely resembles VP1 from polyomaviruses. Surface loops contain t
he sites of sequence variation among HPV types and the locations of dominan
t neutralizing epitopes. The ease with which small virus-like particles may
be obtained from L1 expressed in E. coli makes them attractive candidate c
omponents of a papillomavirus vaccine. Their crystal structure also provide
s a starting point for future vaccine design.