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J Bacteriol, June 1998, p. 2842-2848, Vol. 180, No. 11
Department of Biology1
and
Department of Chemistry,
Received 20 November 1997/Accepted 9 March 1998
Thin pili of the closely related IncI1 plasmids ColIb-P9 and R64
are required only for liquid mating and belong to the type IV family of
pili. They were sedimented by ultracentrifugation from culture medium
in which Escherichia coli cells harboring ColIb-P9- or
R64-derived plasmids had been grown, and then the pili were purified by
CsCl density gradient centrifugation. In negatively stained thin pilus
samples, long rods with a diameter of 6 nm, characteristic of type IV
pili, were observed under an electron microscope. Gel electrophoretic
analysis of purified ColIb-P9 thin pili indicated that thin pili
consist of two kinds of proteins, pilin and the PilV protein. Pilin was
demonstrated to be the product of the pilS gene. Pilin was
first synthesized as a 22-kDa prepilin from the pilS gene
and subsequently processed to a 19-kDa protein by the function of the
pilU product. The N-terminal amino group of the processed
protein was shown to be modified. The C-terminal segments of the
pilV products vary among six or seven different types, as a
result of shufflon DNA rearrangements of the pilV gene.
These PilV proteins were revealed to comprise a minor component of thin
pili. Formation of PilV-specific cell aggregates by ColIb-P9 and R64
thin pili was demonstrated and may play an important role in liquid
mating.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Purification and Characterization of Thin Pili of
IncI1 Plasmids ColIb-P9 and R64: Formation of PilV-Specific
Cell Aggregates by Type IV Pili
*
Corresponding author. Mailing address: Department of
Biology, Tokyo Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan. Phone: 81-426-77-2568. Fax: 81-426-77-2559. E-mail: komano-teruya{at}c.metro-u.ac.jp.
J Bacteriol, June 1998, p. 2842-2848, Vol. 180, No. 11
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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