The following text describes a protein:
Function:
Component of the translocation and assembly module (TAM), which facilitates the insertion and assembly of specific beta-barrel proteins into the outer membrane. Promotes the assembly and secretion across the outer membrane of a subset of autotransporters, such as Ag43. Involved in the assembly of the outer membrane usher protein FimD. In vitro, when TAM is reconstituted into preformed liposomes, it can promote the assembly of several outer membrane proteins, including OmpA, EspP, Ag43 and FadL. TamA is sufficient to catalyze a low level of outer membrane protein (OMP) assembly, but both TamA and TamB are required for efficient OMP assembly. TamB may regulate TamA activity. It could regulate conformational changes in TamA to drive its function in OMP assembly. It could also act as a chaperone that facilitate the transport of nascent membrane proteins across the periplasm to TamA in the outer membrane; In addition, is involved in outer membrane lipid homeostasis. Likely transports phospholipids between the inner membrane and the outer membrane. It would provide a bridge-like structure that protects phospholipids as they travel across the periplasm. One possible explanation for the apparent dual function of TAM is that TamB is a somewhat generic transporter of hydrophobic molecules; TamB, YdbH and YhdP are redundant, but not equivalent, in performing an essential function for growth and maintaining lipid homeostasis in the outer membrane. The transport functions of TamB and YhdP could be differentiated according to the fatty acid saturation state of the phospholipids, with TamB transporting more unsaturated phospholipids and YhdP more saturated phospholipids. Any of these three proteins is sufficient for growth.
Miscellaneous:
MISCELLANEOUS: TamB is widely distributed across the majority of Gram-negative bacterial lineages and is far more widely distributed than its partner TamA.
Subcellular Localization:
Cell inner membrane; Single-pass membrane protein; Periplasmic side.
Domain:
The periplasmic domain is elongated (up to 160 Angstroms long) and forms contacts with the N-terminal POTRA domains of TamA. The C-terminal region mimics outer membrane protein beta strands. This region (residues 963-1138) consists of a concave, taco-shaped beta sheet with a hydrophobic interior, which can accommodate and shield the hydrophobic side of an amphipathic beta strand, potentially allowing TamB to chaperone nascent membrane proteins across the periplasm to TamA in the outer membrane.
Sequence:
MSLWKKISLGVVIVILLLLGSVAFLVGTTSGLHLVFKAADRWVPGLDIGKVTGGWRDLTLSDVRYEQPGVAVKAGNLHLAVGLECLWNSSVCINDLALKDIQVNIDSKKMPPSEQVEEEEDSGPLDLSTPYPITLTRVALDNVNIKIDDTTVSVMDFTSGLNWQEKTLTLKPTSLKGLLIALPKVAEVAQEEVVEPKIENPQPDEKPLGETLKDLFSRPVLPEMTDVHLPLNLNIEEFKGEQLRVTGDTDITVSTMLLKVSSIDGNTKLDALDIDSSQGIVNASGTAQLSDNWPVDITLNSTLNVEPLKGEKVKLKMGGALREQLEIGVNLSGPVDMDLRAQTRLAEAGLPLNVEVNSKQLYWPFTGEKQYQADDLKLKLTGKMTDYTLSMRTAVKGQEIPPATITLDAKGNEQQVNLDKLTVAALEGKTELKALLDWQQAISWRGELTLNGINTAKEFPDWPSKLNGLIKTRGSLYGGTWQMDVPELKLTGNVKQNKVNVDGTLKGNSYMQWMIPGLHLELGPNSAEVKGELGVKDLNLDATINAPGLDNALPGLGGTAKGLVKVRGTVEAPQLLADITARGLRWQELSVAQVRVEGDIKSTDQIAGKLDVRVEQISQPDVNINLVTLNAKGSEKQHELQLRIQGEPVSGQLNLAGSFDRKEERWKGTLSNTRFQTPVGPWSLTRDIALDYRNKEQKISIGPHCWLNPNAELCVPQTIDAGAEGRAVVNLNRFDLAMLKPFMPETTQASGIFTGKADVAWDTTKEGLPQGSITLSGRNVQVTQTVNDAALPVAFQTLNLTAELRNNRAELGWTIRLTNNGQFDGQVQVTDPQGRRNLGGNVNIRNFNLAMINPIFTRGEKAAGMVSANLRLGGDVQSPQLFGQLQVTGVDIDGNFMPFDMQPSQLAVNFNGMRSTLAGTVRTQQGEIYLNGDADWSQIENWRARVTAKGSKVRITVPPMVRMDVSPDVVFEATPNLFTLDGRVDVPWARIVVHDLPESAVGVSSDVVMLNDNLQPEEPKTASIPINSNLIVHVGNNVRIDAFGLKARLTGDLNVVQDKQGLGLNGQINIPEGRFHAYGQDLIVRKGELLFSGPPDQPYLNIEAIRNPDATEDDVIAGVRVTGLADEPKAEIFSDPAMSQQAALSYLLRGQGLESDQSDSAAMTSMLIGLGVAQSGQIVGKIGETFGVSNLALDTQGVGDSSQVVVSGYVLPGLQVKYGVGIFDSIATLTLRYRLMPKLYLEAVSGVDQALDLLYQFEF