This is the C-terminal domain CetZ proteins, which are tubulin-like proteins involved in control cell shape in Archaea and some bacteria [1]. CetZ proteins are related with Tubulin/FtsZ, and has the Tubulin GTPase domain (Pfam:PF00091) at the N-terminal. This domain has a two-layer alpha-beta structure with an alpha-helical extension.

1: CetZ tubulin-like proteins control archaeal cell shape. Duggin IG, Aylett CH, Walsh JC, Michie KA, Wang Q, Turnbull L, Dawson EM, Harry EJ, Whitchurch CB, Amos LA, Lowe J; Nature. 2015;519:362-365. PMID:25533961