The cytosolic N-terminal region of heterologously-expressed transmembrane channel-like protein 1 (TMC1) can be cleaved in HEK293 cells
Fig 6
The amino acid sequence of Nt partial protein of mTMC1 resembles those of basic-region leucine zipper (bZIP) transcription factors.
(A) An alignment of amino acid sequences of bZIP transcription factors of mice (C/EBPα, CREB1α, HLF, DBP, TEF, c-Jun, c-Fos, and ATF6α) and the Nt partial protein (M1-E127) of mTMC1 (amino acid residues from 37th proline to 127th glutamate are shown). Abbreviations are C/EBP, CCAAT/enhancer binding protein; CREB, cyclic AMP responsive element binding protein; HLF, hepatic leukemia factor; DBP, albumin D-box binding protein; TEF, thyrotroph embryonic factor; and ATF, Activating transcription factor. c-Jun and c-Fos are components of the AP-1 site binding protein. The GenBank accession numbers of the amino acid sequences of C/EBPα, CREB1α, HLF, DBP, TEF, c-Jun, c-Fos, and ATF6α are NP_031704.2, NP_598589.2, NP_766151.1, NP_058670.2, NP_059072.1, NP_034721.1, NP_034364.1, and NP_001074773.1, and respectively. The conserved basic amino acid residues which are present in mTMC1 are labeled with plus (+) signs. The hydrophobic residues of mTMC1 at the “a” and “d” positions of the leucine zipper-like sequence are labeled with phi (φ) signs. Green lines indicate the regions of predicted coiled-coils in mTMC1. Each region of bZIP transcription factors was assigned according to a reference [36]. (B) A schematic diagram of a dimer of bZIP transcription factors after [37] (left). The bZIP transcription factors form a dimer (Homodimer or heterodimer). Green cylinders are coiled-coils. The basic region (deep blue) is the basic (positively-charged) residue-rich DNA-binding region. Hydrophobic residues which form the leucine zipper at the “a” and “d” positions are colored purple. Charged residues at the “e” and “g” positions are colored light blue. A cross section of the leucine zipper is shown on the right. (B) A schematic diagram of C/EBP, an example of bZIP transcription factors. (C) An assumed schematic diagram of mTMC1 partial protein (left). Cross sections of five heptads are shown on the right.