1.C.76 The Pore-forming Maculatin Peptide (Maculatin) Family Maculatins exist in four isoforms (1.1, 1.2, 2.1 and 3.1). They form pores in lipid bilayers (Ambroggio et al., 2005). Each of these small peptides consists of a single α-helical TMS per polypeptide chain which oligomerize to produce pores in biological membranes. These can cause leakage and thus kill the cell. Maculatin forms an ensemble of structurally diverse temporarily functional low-oligomeric pores, which mimic integral membrane protein channels in structure (Wang et al. 2016). These pores continuously form and dissociate in the membrane. Membrane permeabilization is dominated by hexa-, hepta- and octamers, which conduct water, ions and small dyes. Pores form by consecutive addition of individual helices to a transmembrane helix or helix bundle. The diversity of the pore architectures-formed by a single sequence-may be a key feature in preventing bacterial resistance and could explain why sequence-function relationships in AMPs remain elusive (Wang et al. 2016). Peptides, indolicidin, aurein 1.2, magainin II, cecropin A and LL-37 all cause a general acceleration of essential lipid transport processes without altering the overall structure of the lipid membranes or creating organized pore-like structures (Nielsen et al. 2020). Rapid scrambling of the lipid composition associated with enhanced lipid transport may trigger lethal signaling processes and enhance ion transport.
This family belongs to the Cecropin Superfamily.
References:
Ambroggio, E.E., F. Separovic, J.H. Bowie, G.D. Fidelio, and L.A. Bagatolli. (2005). Direct visualization of membrane leakage induced by the antibiotic peptides: maculatin, citropin, and aurein. Biophys J. 89: 1874-1881.
Fernandez DI., Gehman JD. and Separovic F. (2009). Membrane interactions of antimicrobial peptides from Australian frogs. Biochim Biophys Acta. 1788(8):1630-8.
Mechler, A., S. Praporski, K. Atmuri, M. Boland, F. Separovic, and L.L. Martin. (2007). Specific and selective peptide-membrane interactions revealed using quartz crystal microbalance. Biophys. J. 93: 3907-3916.
Nielsen, J.E., V.A. Bjørnestad, V. Pipich, H. Jenssen, and R. Lund. (2020). Beyond structural models for the mode of action: How natural antimicrobial peptides affect lipid transport. J Colloid Interface Sci 582: 793-802. [Epub: Ahead of Print]
Rozek, T., K.L. Wegener, J.H. Bowie, I.N. Olver, J.A. Carver, J.C. Wallace, and M.J. Tyler. (2000). The antibiotic and anticancer active aurein peptides from the Australian Bell Frogs Litoria aurea and Litoria raniformis the solution structure of aurein 1.2. Eur J Biochem 267: 5330-5341.
Sani, M.A., A.P. Le Brun, and F. Separovic. (2020). The antimicrobial peptide maculatin self assembles in parallel to form a pore in phospholipid bilayers. Biochim. Biophys. Acta. Biomembr 1862: 183204. [Epub: Ahead of Print]
Wang, G., Y. Li, and X. Li. (2005). Correlation of three-dimensional structures with the antibacterial activity of a group of peptides designed based on a nontoxic bacterial membrane anchor. J. Biol. Chem. 280: 5803-5811.
Wang, Y., C.H. Chen, D. Hu, M.B. Ulmschneider, and J.P. Ulmschneider. (2016). Spontaneous formation of structurally diverse membrane channel architectures from a single antimicrobial peptide. Nat Commun 7: 13535.
Examples:
TC#	Name	Organismal Type	Example
1.C.76.1.1	Maculatin 1.1 (21 aas); similar to caerin (1.C.52.1.9) (Fernandez et al., 2008; Mechler et al., 2007). Maculatins self assemble in parallel to form pores in phospholipid bilayers (Sani et al. 2020).	Metazoa	*Maculatin 1.1 of Litoria genimaculata* (P82066)**

1.C.76.1.2	*Maculatin-2.1 of 18 aas and 1 TMS. Maculatins self assemble in parallel to form pores in phospholipid bilayers (Sani et al.* 2020).**		*Maculatin-2.1 of Litoria genimaculata* (Green-eyed tree frog)**

1.C.76.1.3	Aurein-1.2 of 13 aas and 1 TMS. It shows antimicrobial activity against B. cereus, L. lactis, L.i nnocua, M. luteus, P. multocida, S. aureus, S. epidermidis and S. uberis and has anticancer activity (Rozek et al. 2000). It probably acts by disturbing membrane functions with its amphipathic structure. The 3d structure in a micelle is known (Wang et al. 2005).		Aurein-1.2 of Litoria aurea (bell frog)

1.C.76.1.4	Citropin-1.2 of 16 aas and 1 TMS.		*Citropin-1.2 of Litoria citropa* (Australian blue mountains tree frog)**

1.C.76.1.5	*Uperin-2.3 of 19 aas and 1 TMS. It shows medium antibacterial activities against B. cereus, L. mesenteriodes* and S. uberis.**		*Uperin-2.3 of Uperoleia inundata* (Floodplain toadlet)**