Affiliation:
1. Edward Mallinckrodt Department of Pediatrics and Department of Molecular Microbiology, Washington University School of Medicine, and Division of Infectious Diseases, St. Louis Children's Hospital, St. Louis, Missouri
Abstract
ABSTRACT
Nontypeable
Haemophilus influenzae
is a gram-negative commensal organism that is commonly associated with localized respiratory tract disease. The pathogenesis of disease begins with colonization of the nasopharynx, a process that likely depends on bacterial adherence to respiratory epithelial cells. Hia is the major adhesin expressed by a subset of nontypeable
H. influenzae
strains and promotes efficient adherence to a variety of human epithelial cell lines. Based on previous work, Hia is transported to the surface of
Escherichia coli
transformants and is capable of mediating
E. coli
adherence without the assistance of other
H. influenzae
proteins. In the present study, we examined the mechanism of Hia secretion. PhoA fusions, deletional mutagenesis, and N-terminal amino acid sequencing established that the signal for Hia export from the cytoplasm resides in the first 49 amino acids, including a 24-amino-acid stretch with striking similarity to the N terminus of a number of proteins belonging to the autotransporter family. Immunoelectron microscopy demonstrated that the Hia internal region defined by amino acids 221 to 779 is exposed on the bacterial surface. Secondary-structure analysis predicted that the C terminus of Hia forms a β-barrel with a central hydrophilic channel, and site-specific mutagenesis and fusion protein analysis demonstrated that the C terminus targets Hia to the outer membrane and functions as an outer membrane translocator, analogous to observations with autotransporter proteins. In contrast to typical autotransporter proteins, Hia undergoes no cleavage between the internal and C-terminal domains and remains fully cell associated. Together, these results suggest that Hia is the prototype of an important subfamily of autotransporter proteins.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
92 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献