The cytoskeleton is a dynamic network of proteins, which are required by all cells for cell division, growth, and maintenance of cell shape. A major group of cytoskeleton proteins present in nearly all cells are the tubulin superfamily proteins. Archaea, the third domain of life, encode a great diversity of tubulin superfamily proteins, including FtsZ and the tubulins that are more similar to those in eukaryotes. Recently a new group of cytoskeletal proteins was found in archaea, named CetZ, which show characteristics in common with both tubulin and FtsZ and are involved in cell shape regulation. They form dynamic cytoplasmic filaments at or near the cell envelope, which are required for cell shape determination. However, the mechanisms by which CetZ proteins lead to remodeling of the cell envelope to modulate cell shape remain unknown. Based on crystal structures of CetZ proteins and their likely manner of self-association, we initiated a structure-function analysis of CetZ interactions and function in vivo and in vitro. Point mutants that disrupt the longitudinal and lateral interactions were introduced into the Haloferax volcanii CetZ1 protein, designed to target putative functional interactions in self-association and putative membrane association. Light scattering and TEM were used as an approach to analyze the polymerization cycle and structural features of CetZ polymers, correlating these to the in vivo structures observed by high- and super-resolution fluorescence microscopy. The functional activities of CetZ1 in H. volcanii will help researchers better understand the fundamental processes that contribute to archaea cell shape control. Characterizing CetZ1 proteins and their interactions with other proteins and lipids will also aid in our understanding of how these proteins regulate cell shape, as well as a major cytoskeletal component in archaea.