Flagella of some of the actinoplanete genera were purified and the mol
ecular sizes of their flagellin subunits compared by SDS-PAGE analysis
to flagellins of cells of other bacteria. Several species of Actinopl
anes have a major flagellar protein of subunit sizes of 42-43 kDa and
a lesser amount of a second protein, possibly a minor flagellin subuni
t, of 60 kDa, The flagellar protein sizes of other actinoplanetes rang
ed from 32-43 kDa (major) and 48-58 kDa (minor), Antibodies formed aga
inst the 42-kDa protein of A. rectilineatus showed cross-reactivity in
Western blots against flagellar proteins of spores of other Actinopla
nes species, two species of Dactylosporangium and an Ampullariella spe
cies, Cross-reactivity was also observed with motile cells of two othe
r actinomycetes, Arthrobacter atrocyaneus and a Geodermatophilus speci
es, and with Bacillus subtilis, No cross-reactivity was observed with
Escherichia coli or Planomonospora parontospora flagellar proteins, Th
e amino acid composition and partial N-terminal sequence of the 42-kDa
flagellar protein of A. rectilineatus was compared to literature data
for other bacterial flagellins and found to be most similar to B. sub
tilis 168.