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Journal of Bacteriology, September 1998, p. 4613-4620, Vol. 180, No. 17
Department of Biology, Tokyo Metropolitan
University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
Received 13 April 1998/Accepted 24 June 1998
The thin pili of IncI1 plasmid R64, which is required for
conjugation in liquid media, belong to the type IV pilus family. They
consist of a major subunit, the pilS product, and a minor component, one of the seven pilV products. The
pilS product is first synthesized as a 22-kDa prepilin,
processed to a 19-kDa mature pilin by the function of the
pilU product, and then secreted outside the cell. The
mature pilin is assembled to form a thin pilus with the
pilV product. To reveal the relationship between the
structure and function of the pilS product, 27 missense
mutations, three N-terminal deletions, and two C-terminal deletions
were constructed by PCR and site-directed mutagenesis. The
characteristics of 32 mutant pilS products were analyzed.
Four pilS mutant phenotype classes were identified. The
products of 10 class I mutants were not processed by prepilin
peptidase; the extracellular secretion of the products of two class II
mutants was inhibited; from 11 class III mutants, thin pili with
reduced activities in liquid mating were formed; from 9 class IV
mutants, thin pili with mating activity similar to that of the
wild-type pilS gene were formed. The point mutations of the
class I mutants were distributed throughout the prepilin sequence,
suggesting that processing of the pilS product requires the
entire prepilin sequence.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutational Analysis of Plasmid R64 Thin Pilus Prepilin: the
Entire Prepilin Sequence Is Required for Processing by Type IV
Prepilin Peptidase
and
*
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.
Present address: Department of Biochemistry, Robert Wood Johnson
Medical School, University of Medicine and Dentistry of New Jersey,
Piscataway, NJ 08854.
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