The following text describes a protein:
Function:
Found in functional membrane microdomains (FMM) that may be equivalent to eukaryotic membrane rafts. FMMs are highly dynamic and increase in number as cells age. FloA and FloT function is partially redundant; double deletions have marked synthetic phenotypes. Flotillins are thought to be important factors in membrane fluidity, especially during periods of rapid growth in rich media (Probable). Whether specific proteins are associated with FMMs is controversial; in one study FloT rafts have been shown to include proteins involved in adaptation to stationary phase, while FloA-FloT rafts include proteins involved in differentiation including sporulation, biofilm formation and DNA uptake competence. Another (more finely resolved) study only showed association of NfeD2 with FloT rafts of all the proteins examined. Aids homooligomerization of KinC and KinD but not KinB, may prevent incorrect hetero-association of the above kinases. Simultaneous overexpression of both FloA and FloT leads to defects in cell division and differentiation, in part caused by stabilization of FtsH and its subsequent increased ability to degrade proteins. Cells make more biofilm, are about half as long, have less EzrA and more frequent Z-rings. Involved in spatial organization of membranes, perhaps recruiting proteins (e.g. NfeD2) to specific membrane regions (Probable). Plays a role in phosphorylation of master regulator Spo0A, an early sporulation event. Plays a non-redundant role with dynamin-like protein A (dynA) in membrane dynamics and cell shape.
Subcellular Localization:
Cell membrane. Membrane raft. Note=Tethered to the membrane by a hairpin loop that inserts into the cell membrane. A few foci are seen on the cell membrane during exponential growth, more are seen as cells enter stationary phase. Restricted to the mother cell during sporulation. Foci form a spiral track on the cell membrane and move in the cell. Associated with high bouyancy, cardiolipin- and phosphatidylglycerol-rich membrane fractions, association is not obligatory. Present in detergent-resistant membrane (DRM) fractions, approximately 6 dynamic foci per cell; colocalizes with KinC and sometimes with FloA in DRMs. Foci are lost when cells are treated with squalene synthase inhibitor zaragozic acid. Found in discrete, highly mobile foci, often colocalizes with NfeD2 but rarely with FloA. Forms discrete foci on the cell membrane, about 20% of foci are at the septal site. At the septa colocalizes with FloA and FtsH. Colocalizes with FtsX, OppA, SdhA and SecY in DRMs. Careful analysis gives an average of 13 FloA and 6 FloT foci per cell; FloA foci are smaller that FloT foci. Another study shows FloA and FloT foci are similar in size, forming membrane assemblies of 85-110 nm. FloA are more mobile than FloT foci and they do not overlap. This study found no evidence of colocalization of FloA with FloT, and nearly complete colocalization of FloT with NfeD2.
Domain:
A hairpin loop (about residues 4-24) tethers the protein in the inner membrane. The isolated PHB domain (also called SPFH) oligomerizes, but does not bind lipids. The C-terminal 24 residues are not required for correct localization, but the last 300 residues are required. The C-terminus determines the oligomerization state of the protein; there are few large foci for FloT. Swapping with the C-terminus of FloA leads to many smaller foci.
Sequence:
MTMPIIMIIGVVFFLLIALIAVFITKYRTAGPDEALIVTGSYLGNKNVHVDEGGNRIKIVRGGGTFVLPVFQQAEPLSLLSSKLDVSTPEVYTEQGVPVMADGTAIIKIGGSIGEIATAAEQFLGKSKDDREQEAREVLEGHLRSILGSMTVEEIYKNREKFSQEVQRVASQDLAKMGLVIVSFTIKDVRDKNGYLESLGKPRIAQVKRDADIATAEADKETRIKRAEADKDAKKSELERATEIAEAEKINQLKMAEFRREQDTAKANADQAYDLETARARQQVTEQEMQVKIIERQKQIELEEKEILRRERQYDSEVKKKADADRYSVEQSAAAEKAKQLAEADAKKYSIEAMAKAEAEKVRIDGLAKAEAEKAKGETEAEVIRLKGLAEAEAKEKIAAAFEQYGQAAIFDMIVKMLPEYAKQAAAPLSNIDKITVVDTGGSGESSGANKVTSYATNLMSSLQESLKASSGIDVKEMLENFSGKGNVKQSINELTNEIKEAKTIQKSE