Defense Date

8-8-2013

Graduation Date

2013

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

Committee Chair

Joseph R McCormick

Committee Member

Jana L Patton-Vogt

Committee Member

Nancy J Trun

Committee Member

Justin R Nodwell

Keywords

Cell division, FtsEX, FtsZ, SepF, SlzA, Streptomyces coelicolor

Abstract

For various bacteria, an assortment of proteins, many of which are nonessential for division, bind the C-terminal tip of FtsZ to help stabilize the Z-ring and tether it to the cytoplasmic membrane. S. coelicolor produces aerial hyphae that contain numerous, evenly-spaced Z-rings that jointly constrict to form a chain of spores. Our understanding of this developmental process is complicated by the lack of known FtsZ-interacting proteins. To date, only two proteins, SsgA and SsgB, have been found to aid in Z-ring localization. For this study, the 399 amino acid FtsZ, multiple FtsZ C-terminal tip variants, and four putative FtsZ-associated proteins were analyzed to better understand how Z-rings assemble and function during development-associated cell division. Truncation of the conserved C-terminal tip and alanine-scanning mutagenesis revealed that this region is essential for FtsZ function. A strain expressing the non-functional FtsZ(F397A) variant and another lacking SepF, displayed a phenotype similar to that of the ftsZ-null strain: septation was, at least, dramatically reduced in vegetative filaments and completely blocked in aerial filaments. SepF was found to localize to the site of septation, consistent with the speculation that it aids in Z-ring constriction. SepF was also shown to dimerize in an in vivo assay, and it interacts with FtsZ through an interaction at the CTT to stimulate protofilament formation in vitro. On the other hand, strains lacking FtsE and FtsX displayed no discernible phenotype, and no interactions were found among FtsE, FtsX, and FtsZ in the bacterial two-hybrid analysis. Lastly, the small leucine zipper protein A (slzA) gene, which encodes a 69 amino acid coiled-coil protein with a leucine zipper motif, was identified and characterized. The location of this gene immediately upstream of smc suggests a possible role in DNA segregation, while the structure of the protein suggests that it could be analogous to E. coli division protein ZapB. The slzA-null strain was not overtly blocked in either division or DNA segregation. Consistent with the prediction that it is a leucine zipper protein, SlzA strongly interacted with itself, but, like ZapB, it did not interact with FtsZ. These data reveal new information to better understand how Z-rings are formed, stabilized, and constrict during vegetative and development-associated cell division in S. coelicolor.

Format

PDF

Language

English

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