Bacterial chemotaxis is one of the best-known signal transduction systems. Levels of attractants and repellents are sensed in the surrounding environment by various chemoreceptors. The signal is passed to the excitation pathway via the transfer of a phosphoryl group from the receptor-associated histidine kinase CheA to the response regulator CheY. Phospho-CheY binds to the flagellar motor switching the direction of rotation of the flagella and thus allowing the cell to move towards or away from the attractant or repellent. The phosphatase CheZ removes the phosphoryl group from phospho-CheY restoring default flagellar rotation. Adaptation to stimuli occurs via addition of methyl groups to the receptor by the CheR methyltransferase and their removal by the CheB methylesterase.

In order to leam more about the diversity of signal transduction, we used bioinformatics to analyze two of the key proteins in the chemotaxis pathway: the singledomam response regulator CheY and multi-domain methyl-accepting chemotaxis proteins (MCPs). Database searches revealed more than 50 known and putative CheY proteins and CheY-like domains with alignment analysis revealing overall conservation in protein folding. From published papers, critical residues were identified that played important roles in phosphorylation and interaction with CheA, CheZ and FliM proteins.

Topological studies classified all known and putative MCPs into six distinct classes. Analysis of the C-terminal signaling domain showed that the two methylation regions (K1 and Rl) as well as the highly conserved domain (HCD) had a similar fold and a high degree of conservation. PSI-BLAST analysis showed a statistically significant relationship (E < .001) between the N-terminal sensing domain of bacterial chemporeceptors and the sensing domains from histidine and serine/threonine kinases.

LLU Discipline

Microbiology and Molecular Genetics


Microbiology, Molecular Biology and Biochemistry


Graduate School

First Advisor

Igor B. Zhulin

Second Advisor

Mark S. Johnson

Third Advisor

Anthony J. Zuccarelli

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Bacterial Proteins -- analyis; Computational Biology; DNA Sequence Analysis; Genetics, Biochemical



Page Count

vii; 116

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


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Loma Linda University. Del E. Webb Memorial Library. University Archives