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IN PRESS: Journal of Bacteriology. 1997. 179(24):XXX-XXX.

MYXOCOCCUS XANTHUS sasS ENCODES A SENSOR HISTIDINE KINASE REQUIRED FOR EARLY DEVELOPMENTAL GENE EXPRESSION.

Chun Yang and Heidi B. Kaplan

Department of Microbiology and Molecular Genetics

University of Texas Medical School at Houston

(For the full text, click here to connect to Dr.Heidi Kaplan's home page.)

ABSTRACT

Initiation of Myxococcus xanthus multicellular development requires

integration of information concerning the cell's nutrient status and cell

density. A gain-of-function mutation, sasB7, that bypasses both the

starvation and high cell density requirements for developmental expression

of the 4521 reporter gene, maps to the sasS gene. The wild-type sasS gene

was cloned and sequenced. This gene is predicted to encode a sensor

histidine protein kinase that appears to be a key element in the

transduction of starvation and cell density inputs. The sasS null mutants

express 4521 at a basal level, form defective fruiting bodies and exhibit

reduced sporulation efficiencies. These data indicate that the wild-type

sasS gene product functions as a positive regulator of 4521 expression and

participates in M. xanthus development. The N-terminus of SasS is

predicted to contain two transmembrane domains that would locate the

protein to the cytoplasmic membrane. The sasB7 mutation, an E139K missense

mutation, maps to the predicted N-terminal periplasmic region. The

C-terminus of SasS contains all of the conserved residues typical of the

sensor histidine protein kinases. SasS is predicted to be the sensor

protein in a two-component system that integrates information required for

M. xanthus developmental gene expression.

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Heidi B. Kaplan, Ph.D.

Assistant Professor

Department of Microbiology and Molecular Genetics

6431 Fannin, 1.765 JFB

University of Texas Medical School

Houston, TX 77030

Ph. 713-500-5448

Fx. 713-500-5499