Motion in Immunoglobulin (Fab Elbow Joint) [igelbow]

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Classification Known Domain Motion, Neither Hinge nor Shear Mechanism [D-n-2]

Structures
1MCP Conformation 1 [ PartsList ]
2FB4 Conformation 4 [ PartsList ]
2FBJ Conformation 3 [ PartsList ]
4FAB Conformation 2 [ PartsList ]

Description
Hinge motion in linking peptides. Ball and socket joint forms interface between domains. Range of rotations up to 50 degrees allowed. Data bank indentifiers for only 4 of the many representative immunoglobulin stuctures are indicated. The domain motion observed in the immunoglobulins involves, so far as is known at present, a unique combination of hinge and shear motions. In the immunoglobulins the VL domain is linked by an extended peptide to the CL domain, and VH is similarly linked to CH1. VL and VH pack together, as do CL and CH1. The VL-VH dimer can freely rotate, relative to the CL-CH1 dimer, over a range of ~50 degrees in a manner described as 'elbow motion.' Elbow motion involves localized deformations in the two peptides that link the V and C dimers. These deformations are similar to those in the hinged domain closures described in the previous sections. However, the elbow motion also involves an unusual type of shear motion: two large residues in CH1, a Pro and Phe, pack closely together, forming a 'ball,' and three residues in VH spread out as part of a beta-sheet, forming a 'socket'. The three VH and two CH1 residues are packed together and move relative to each other in a manner similar to a socket moving over a ball. Unlike shear motions, which are characterized by close-packed interfaces of interdigitating sidechains, the ball-and-socket joint has a 'smooth' interface, in which the side chains do not interdigitate. This interface facilitates motion over a wide range of relative orientations. It also permits greater flexibility than found in shear motions: the 'socket' residues can move up to 4.5 A relative to those in the 'ball,' rather than the 1.5 to 2.0 A displacement usually found at a shearing interface.

Particular values describing motion
Experimental Methods = x (Traditional x-ray)
Creation Date = 19970822
Modification Date = 19970822

References
S Vasudevan and D R Rose. "Conformational Flexibility in Antibodies and their Fragments," unpublished(?) manuscript. [Medline info for 95319545]
A M Lesk and C Chothia (1988). Elbow Motion in the immunoglobulins involves a molecular ball and socket joint. Nature. 335: 188-190. [Medline info for 95319545]
W S Bennett and R Huber (1984). Structural and Functional Aspects of Domain Motion in Proteins. Crit. Rev. Biochem. 15: 291-384. [Medline info for 95319545]

Data and Graphics
Graphic-2 Another picture of the ball-and-socket joint.
Graphic-1 Ball-and-socket joint (Copyright Biochemistry, 1994)

Morphs

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Best representative
Morph Morph name Structure #1 Structure #2 Residues
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Copyright 1995-2005 M. Gerstein, W. Krebs, S. Flores, N. Echols, and others
Email: Mark.Gerstein _at_ yale.edu