RBP circulates in the plasma bound to its carrier protein transthyretin (TTR) and this protein-protein complex is thought to interact with specific cell receptors to deliver retinol to the target cells. Because of its role in the specific transport of an essential vitamin, this lipocalin has been the focus of a great deal of research.

Based on holo-RBP affinity for TTR and on their plasma concentrations (2 µM and 3.6–4.5 µM, respectively), it has been estimated that about 95% of circulating RBP is associated with TTR [6, 7, 8]. Plasma TTR levels rise after birth, reaching a concentration of 20–40 mg/dL in adults, and then TTR levels decrease after 50 years of age [9].

Transthyretin (TTR) is a tetrameric transport protein highly conserved through vertebrate evolution and synthesized in the liver, choroid plexus, and retinal pigment epithelium. TTR transports the thyroid hormone thyroxine and the retinol-binding protein (RBP) bound to retinol (vitamin A).

1999年2月3日 · Whether ultimately utilized as retinoic acid, retinal, or retinol, vitamin A is transported to the target cells as all-trans-retinol bound to retinol-binding protein (RBP). Circulating in the plasma, RBP itself is bound to transthyretin (TTR, previously referred to as thyroxine-binding prealbumin).

Besides T 4, TTR is also the main carrier of retinol (vitamin A), by establishing a 1:1 molar complex with retinol binding protein (RBP), with binding being limited to a maximum of two RBP molecules per TTR tetramer (Fig. 1B). Accordingly, the main acknowledged physiological function of TTR is the transport of the thyroid hormone (TH) thyroxine ...

1997年8月1日 · The mechanism by which cells take up retinol from retinol-binding protein (RBP) and the role of the RBP-transthyretin (TTR) complex remain unclear. Here we report on retinol uptake through the RBP-TTR complex by primary cultured rat hepatocytes (parenchymal cells, PC) and nonparenchymal cells (NPC) …

2004年12月1日 · Retinol transport complex consisting of retinol-binding protein (RBP) and transthyretin (TTR) is involved in the transport of retinol (vitamin A) and thyroxine (T 4) in the human plasma. RBP is a 21-kDa single polypeptide chain protein, synthesized in the liver, which binds and transports retinol to the target organs.

1995年1月13日 · Tissue needs for retinoids are believed to be satisfied through the delivery in the circulation of retinol by its specific plasma transport protein, retinol-binding protein (RBP), which circulates as a 1-to-1 protein complex with transthyretin (TTR). The binding of RBP to TTR is thought to prevent filtration of retinol-RBP in the kidney and to ...

1999年3月2日 · Whether ultimately utilized as retinoic acid, retinal, or retinol, vitamin A is transported to the target cells as all-trans-retinol bound to retinol-binding protein (RBP). Circulating in the plasma, RBP itself is bound to transthyretin (TTR, previously referred to as thyroxine-binding prealbumin).

Retinol-binding protein 4 (RBP4) is an adipokine bound in plasma to transthyretin (TTR), which prevents its glomerular filtration and subsequent catabolism in the kidney. Alterations of this interaction have been suggested to be implicated in the elevation of RBP4 that are thought to contribute to t …