Structure
Proteins from the TGF-beta family are only active as homo- or heterodimer; the two chains being linked by a single disulfide bond. From X-ray studies of TGF-beta-2, it is known that all the other cysteines are involved in intrachain disulfide bonds. As shown in the following schematic representation, there are four disulfide bonds in the TGF-beta's and in inhibin beta chains, while the other members of this family lack the first bond.
interchain | +------------------------------------------|+ | || xxxxcxxxxxCcxxxxxxxxxxxxxxxxxxCxxCxxxxxxxxxxxxxxxxxxxCCxxxxxxxxxxxxxxxxxxxCxCx | | | | | | +------+ +--|----------------------------------------+ | +------------------------------------------+where 'C' denotes a conserved cysteine involved in a disulfide bond.
Read more about this topic: Transforming Growth Factor Beta Superfamily
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