Monomeric, left-handed β-helix antifreeze protein from the spruce budworm Choristoneura fumiferana (PDB accession code 1M8N).

Dimeric, right-handed β-helix antifreeze protein from the beetle Tenebrio molitor (PDB accession code 1EZG). Face-to-face association of β-helices.

A beta helix is a protein structure formed by the association of parallel beta strands in a helical pattern with either two or three faces. The structure is stabilized by inter-strand hydrogen bonds, protein-protein interactions, and sometimes bound metal ions. Both left- and right-handed beta helices have been identified. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Diagram of Β-Pleated sheet and bond structure of protein The β sheet (also β-pleated sheet) is a commonly occurring form of regular secondary structure in proteins, first proposed by Linus Pauling and Robert Corey in 1951. ... Snapshot from a simulation of liquid water. ... Protein-protein interactions refer to the association of protein molecules and the study of these associations from the perspective of biochemistry or networks. ... An ion is an atom, group of atoms, or subatomic particle with a net electric charge. ...

Two-stranded helices

The simplest beta helix contains two "layers" of beta sheets connected by glycine-rich six-residue loops that invariably contain an asparagine to bind one calcium ion per loop. Each layer consists of a nearly-planar series of parallel hydrogen-bonded beta strands and the two layers together enclose a hydrophobic core. Glycine (Gly, G) is a nonpolar amino acid. ... Asparagine is one of the 20 most common natural amino acids on Earth. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ...

Three-stranded helices

Three-stranded beta helices form a distorted triangular prism shape in which each face exhibits parallel inter-strand hydrogen bonding. One of the three sheets that form the repeating structural motif can appear "bent" relative to the other two, which face each other as in the two-stranded helix. Two of the three linking loops between the sheets can be of arbitrary length and can even contain other structural domains; the third is restricted to two resides. A characteristic common hexapeptide repeat found in both left- and right-handed helices is the sequence [LIV] − [GAED] − X₂ − [STAV] − X. Known three-stranded helices are appreciably longer than their two-stranded counterparts. It has been suggested that Supersecondary structure be merged into this article or section. ... Within a protein, a structural domain (domain) is an element of overall structure that is self-stabilizing and often folds independently of the rest of the protein chain. ...

The first beta-helix was observed in the enzyme pectate lyase, which contains a seven-turn helix that reaches 34Å long. The P22 phage tailspike protein, a component of the P22 bacteriophage, has 13 turns and in its assembled homotrimer is 200Å in length. Its interior is close-packed with no central pore and contains both hydrophobic residues and charged residues neutralized by salt bridges. A bacteriophage, artificially coloured red A bacteriophage (from bacteria and Greek phagein, to eat) is a virus that infects bacteria. ... Trimer might refer to: trimer (chemistry), a reaction product composed of three identical molecules trimer (biochemistry), a compound of three macromolecules non-covalently bound This is a disambiguation page: a list of articles associated with the same title. ... A salt bridge, in chemistry, is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (electrochemical cell). ...

Both pectate lyase and P22 tailspike protein contain right-handed helices; left-handed versions have observed in enzymes such as UDP-N-acetylglucosamine acyltransferase and archaeal carbonic anhydrase. Other proteins that contain beta helices include the antifreeze proteins from the beetle Tenebrio molitor (right-handed) and from the spruce budworm, Choristoneura fumiferana (left-handed), where regularly spaced threonines on the β-helices bind to the surface of ice crystals and inhibit their growth. Ribbon diagram of the enzyme TIM. TIM is catalytically perfect, meaning its conversion rate is limited, or nearly limited to its substrate diffusion rate. ... Carbonic anhydrase (carbonate dehydratase) is a family of metalloenzymes (enzymes that contain one or more metal atoms as a functional component of the enzyme) that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ... A man pouring antifreeze into his vehicle. ... Threonine is one of the 20 natural amino acids. ... The acronym ICE can refer to: InterCity Express, a German high-speed train InterCity Express (CityTrain), an interurban train used by QR CityTrain in South East Queensland, Australia Internal combustion engine, a fuel engine In-circuit emulator, a computer hardware device In case of emergency, emergency number in mobile phones...

Beta helices can associate with each other effectively, either face-to-face (mating the faces of their triangular prisms) or end-to-end (forming hydrogen bonds). Hence, β-helices can be used as "tags" to induce other proteins to associate, similar to coiled coil segments. A coiled coil is a structural motif found in many proteins. ...

External links

• SCOP family of right-handed β-helices
• SCOP family of left-handed β-helices
• CATH β-helix protein family

References

• Branden C, Tooze J. (1999). Introduction to Protein Structure 2nd ed. Garland Publishing: New York, NY. pp 84-6.
• Dicker IB and Seetharam S. (1992) "What is Known about the Structure and Function of the Eschericia-coli Protein FirA" Mol. Microbiol., 6, 817-823.
• Kisker C, Schindelin H, Alber BE, Ferry JG and Rees DC. (1996) "A left-handed β-helix revealed by the crystal structure of a carbonic anhydrase from the achaeon Methanosarcina thermophile", EMBO J., 15, 2323-2330. (Left-handed)
• Liou YC, Tocilj A, Davies PL and Jia Z. (2000) Mimicry of ice structure by surface hydroxyls and water of a beta-helix antifreeze protein." Nature, 406, 322-324.
• Leinala EK, Davies PL and Jia Z. (2002) "Crystal Structure of β-Helical Anitfreeze Protein Points to a General Ice Binding Model", Structure, 10, 619-627.
• Raetz CRH and Roderick SL. (1995) "A Left-Handed Parallel β Helix in the Structure of UDP-N-Acetylglucosamine Acyltransferase", Science, 270, 997-1000. (Left-handed)
• Steinbacher S, Seckler R, Miller S, Steipe B, Huber R and Reinemer P. (1994) "Crystal structure of P22 tailspike protein: interdigitated subunits in a thermostable trimer", Science, 265, 383-386. (Right-handed)
• Vaara M. (1992) "Eight bacterial proteins, including UDP-N-acetylglucosamine acyltransferase (LpxA) and three other transferases of Escherichia coli, consist of a six-residue periodicity theme", FEMS Microbiol. Lett, 97, 249-254.
• Yoder MD, Keen NT and Jurnak F. (1993) "New domain motif:the structrue of pectate lyase C, a secreted plant virulence factor", Science, 260, 1503-1507. (Right-handed)