Ca2+-binding Motif of βγ-Crystallins

Abstract

␤␥-Crystallin-type double clamp (N/D)(N/D)XX(S/T)S motif is an established but sparsely investigated motif for Ca2؉ binding. A ␤␥-crystallin domain is formed of two Greek key motifs, accommodating two Ca 2؉ -binding sites. ␤␥-Crystallins make a separate class of Ca 2؉ -binding proteins (CaBP), apparently a major group of CaBP in bacteria. Paralleling the diversity in ␤␥-crystallin domains, these motifs also show great diversity, both in structure and in function. Although the expression of some of them has been associated with stress, virulence, and adhesion, the functional implications of Ca 2؉ binding to ␤␥-crystallins in mediating biological processes are yet to be elucidated.

βA3/A1-crystallin: More than a lens protein

“…Their data support the idea that a common ancestor of urochordates and vertebrates contained a single domain β/γ-precursor gene from which both the Ciona and vertebrate β/γ-crystallins have evolved. Interestingly, the invertebrate members of the superfamily are calcium binding proteins (Srivastava et al, 2014), while the vertebrate lens β/γ-crystallins and a few other members of the superfamily that are expressed in vertebrates have lost this trait or had it greatly attenuated. It seems likely that through a series of gene duplications and fusions in the early vertebrates, the β-crystallins were formed and that the γ-crystallins subsequently arose from a β-crystallin by loss of the intron separating the two motifs comprising the β-crystallin domain (Wistow, 1995).…”

Specific hypersensitive response-associated recognition of new apoplastic effectors fromCladosporium fulvumin wild tomato

“…However, this fold is now known to occur in a variety of functionally diverse proteins representing all major taxonomic groups of organisms (Kappé et al, 2010; Mishra et al, 2014). A key feature of this fold in many microbial members is a double clamp N/DN/DXXS/TS Ca 2+ -binding motif required for structure and/or function (Srivastava et al, 2014). This motif, however, is not present in Ecp4, Ecp7, CfCE72 (CTR) or CfCE44.…”

Mechanistic insights from replica exchange molecular dynamics simulations into mutation induced disordered-to-ordered transition in Hahellin, a βγ-crystallin

“…There are two canonical Ca 2+ binding motifs 37 NDDLSS 42 and 76 DNDASS 81 in Hahellin ligating two Ca 2+ ions. Precisely, the Ca 2+ ligating residues are E9(+x mc ), N77(-x sc ), D39 (+y mc ) and S41 (+z sc ) forming the site 1 and Q55(+x mc ), D38(-x sc ), D78(+y mc ) and S80 (+z sc ) forming the site 2 based on sequence comparison with other known -crystallins [16]. The residues at +x mc and +y mc coordinates through main-chain carbonyls while residues at -x sc and +z sc coordinate through sidechains.…”

“…The residues at +x mc and +y mc coordinates through main-chain carbonyls while residues at -x sc and +z sc coordinate through sidechains. The Ca 2+ binding pocket is further stabilized by hydrogen bonding between the first residue of the motif 1 ( 37 NDDLSS 42 ) and the fifth residue of motif 2 ( 76 DNDASS 81 ) [16]. -crystallin superfamily includes proteins of diverse domain stability.…”

“…[15]. Most of the archaeal and bacterial crystallins such as Protein S, M-crystallin, Clostrillin are ordered well-folded and undergo further stabilization upon binding to Ca 2+ while vertebrate crystallins are highly stable, but display low affinity for Ca 2+ [16,17]. Such structural inconsistency arose curiosity.…”