PDBsum entry 3l9b

Membrane protein

PDB id: 3l9b

Contents

Protein chain

126 a.a. *

Metals

_MG

Waters ×143

* Residue conservation analysis

PDB id:

3l9b

Name:

Membrane protein

Title:

Crystal structure of rat otoferlin c2a

Structure:

Otoferlin. Chain: a. Fragment: c2a domain. Synonym: fer-1-like protein 2. Engineered: yes

Source:

Rattus norvegicus. Rat. Organism_taxid: 10116. Gene: fer1l2, otof. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.95Å R-factor: 0.183 R-free: 0.229

Authors:

S.Helfmann,P.Neumann

Key ref:

S.Helfmann et al. (2011). The crystal structure of the C₂A domain of otoferlin reveals an unconventional top loop region. J Mol Biol, 406, 479-490. PubMed id: 21216247

Date:

04-Jan-10 Release date: 19-Jan-11

Protein chain

Q9ERC5  (OTOF_RAT) -  Otoferlin from Rattus norvegicus

Seq: 1993 a.a.

Struc: 126 a.a.

Enzyme reactions

• Enzyme class: E.C.?

J Mol Biol 406:479-490 (2011)

PubMed id: 21216247

The crystal structure of the C₂A domain of otoferlin reveals an unconventional top loop region.

S.Helfmann, P.Neumann, K.Tittmann, T.Moser, R.Ficner, E.Reisinger.

ABSTRACT

Otoferlin (Otof), whose genetic mutations cause profound deafness in humans, is a protein composed of at least six C(2) domains, which are known as Ca(2)(+)-binding and phospholipid-binding regions. Mammalian ferlin proteins are proposed to act in membrane fusion events, with Otof being specifically required for exocytosis in auditory hair cells. Ferlin C(2) domains exhibit a rather low level of sequence similarity to those of synaptotagmins, protein kinase C isoforms, or phospholipases. Here, we report the crystal structure of the N-terminal C(2) domain of Otof (C₂A) at 1.95-Å resolution. In contrast to previous predictions, we found that this C(2) domain is complete with eight β-strands. Comparing the structure of Otof C₂A to those of other C(2) domains revealed one top loop in Otof to be significantly shorter. This results in a depression of the surface, which is positively charged for the Otof C₂A domain, and contrasts with the head-like protrusion surrounded by a negatively charged "neck" typically found in other C(2) domains. Isothermal titration calorimetry and circular dichroism spectroscopy studies confirmed that Otof C₂A is unable to bind Ca(2+), while the synaptotagmin-1 C₂A domain exhibited Ca(2+) binding under the same conditions. Furthermore, floatation assays revealed a failure of Otof C(2)A to bind to phospholipid membranes. Accordingly, no positively charged β-groove-like surface structure, which is known to bind phosphatidylinositol-4,5-bisphosphate in other C(2) domains, was found at the respective position in Otof C₂A. Taken together, these data demonstrate that the Otof C₂A domain differs structurally and functionally from other C(2) domains.