Block-type polyampholyte intrinsically disordered protein
A novel 327-residue intrinsically disordered protein: 100% predicted disorder, net charge +14.8 at pH 7.4 and only 2 aromatic residues, built as a charged N-terminal region (an acidic block followed by a basic block) joined to a long, hydrophilic, Thr/Ser-rich C-terminal block. A converged 510 ns CALVADOS 2 ensemble shows a chain of typical IDP size and theta-like scaling (Rg 5.08 nm, ν 0.500), organised by one persistent opposite-charge contact within the charged region and none in the C-terminal block, ranked a polyampholyte. No detectable homology in nr, and no flagged structural neighbour in PDB, AlphaFold DB or ESM metagenomic databases.
evo_c4007 is a novel 327-residue intrinsically disordered protein (IDP) built from two parts: a charged N-terminal region, an acidic block followed by a basic block (26 Glu, 14 Asp, 54 Lys and 1 Arg in the chain as a whole), and a long C-terminal block that is hydrophilic and rich in threonine and serine (118 Thr and 67 Ser in total). It uses 15 of the 20 amino acids, has only 2 aromatic residues (1 Phe, 1 Tyr), 2 cysteines and no folded domain. Sequence analysis predicts 100% disorder. A converged CALVADOS 2 simulation shows a chain of typical IDP size in solution: one free-energy basin and no evidence of discrete states. One intramolecular contact is persistent (formed in 99% of frames, mean lifetime 6.72 ns) and joins the acidic and basic blocks of the charged region; the 3 other enriched contact motifs are transient, and none involves the C-terminal block. Throughout this dossier, REF marks the single atomistic reference conformation that seeds the simulation, ENS marks results from the simulated ensemble, and SEQ marks results computed from the sequence alone.
Disordered chains that pair a charge-organised region with a long neutral hydrophilic block are polymer-like building blocks, with electrostatics acting in one part and an inert, sticker-free tail in the other, and this candidate is characterized at both ends. Its net charge is +14.8 at pH 7.4 (pI 9.52), and the isolated chain has predictable dimensions (Rg 5.08 nm, Rh 3.83 nm) that a partner can check by SAXS or DLS; the ensemble also gives distance-versus-separation scaling that can specify a spacer length. The C-terminal block has no enriched intramolecular contact and almost no aromatic or hydrophobic stickers, while the charged region organises itself through opposite-charge contacts, giving a block-type architecture whose assembly and surface behaviour remain untested. It has no detectable homolog in nr, no flagged structural neighbour in PDB, AlphaFold DB or ESM metagenomic databases, and no known bioactive motif, and each use case below comes with a decisive first experiment.
No close family partner in the Atlas yet — this candidate is currently a singleton (family F0006). 7 candidates fall below the same-fold threshold (TM 0.107–0.184); none reaches TM > 0.5. Sequence-level family (F0008) and structure-level family (F0006) disagree — shown combined as F0006.
Note: whole-chain TM-align is less meaningful for disordered chains (flagged in source report) — read this as sequence-and-shape-class kinship, not a folded-protein identity match.
Full composition, motif coordinates, and simulation trajectories are released to evaluating partners on request.
