Premium
Omega loops; nonregular secondary structures significant in protein function and stability
Author(s) -
Fetrow Jacquelyn S.
Publication year - 1995
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.9.9.7601335
Subject(s) - omega , hydrogen bond , dihedral angle , protein folding , chemistry , protein structure , crystallography , folding (dsp implementation) , globular protein , stereochemistry , physics , molecule , biochemistry , quantum mechanics , organic chemistry , electrical engineering , engineering
Omega (ω‐) loops, a nonregular secondary structure found in globular proteins, are characterized by a polypeptide chain that follows a loop‐shaped course in three‐dimensional space. They do not contain repeating backbone dihedral angles or regular patterns of hydrogen bonding; however, many ω‐loops contain a large number of hydrogen bonds, therefore it is not correct to think of ω‐loops as structures lacking in hydrogen bonds. ω‐Loops are found almost exclusively at the protein surface and exhibit amino acid preferences consistent with this observation. Since the first description of ω‐loops in 1986, experiments have been conducted to probe the role of these structures in protein function, stability, and folding. It has become clear that ω‐loops are often involved in protein function and molecular recognition. One motif, an ω‐loop lid, that is flexible and mobile until substrate or inhibitor is bound and which probably plays a role in one or more steps of enzymatic catalysis, has been described in a variety of enzymes. Because they lack the periodic hydrogen bonding patterns of the regular secondary structures, some ω‐loops are well suited for such functional roles in proteins. However, loops with a higher‐than‐aver‐age number of hydrogen bonds or hydrophobic contacts may play roles in protein stability or folding. Rather than determining further geometric definitions of loops, it may be instructional to group them according to their roles in protein structure, i.e., as categories of functional ω‐loops, stability ω‐loops, and folding ω‐loops.—Fetrow, J. S. Omega loops: nonregular secondary structures significant in protein function and stability. FASEB J. 9, 708‐717 (1995)