Interactions of low density lipoprotein receptors with coated pits on human fibroblasts: estimate of the forward rate constant and comparison with the diffusion limit

Journal Article · Tue Sep 01 00:00:00 EDT 1981 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.78.9.5695· OSTI ID:5301025

Goldstein, B ^[1]; Wofsy, C; Bell, G

---

1. Los Alamos National Lab., NM

We present a theoretical study of the interaction of low density lipoprotein (LDL) receptors with coated pits. From published experiments we estimate that the forward rate constant, k/sub +/, for the binding of a LDL receptor to a coated pit on a human fibroblast at 37/sup 0/C is greater than or equal to 3 x 10/sup -10/ cm/sup 2//sec, and the mean time an LDL receptor spends on the cell surface before being captured by a coated pit, t/sub c/, is less than or equal to 1.8 min. If, when an LDL receptor enters, it remains within the coated pit until the coated pit pinches off to form a coated vesicle, then k/sub +/ = 3 x 10/sup -10/ cm/sup 2//sec and t/sub c/ = 1.8 min. We derive expressions for the diffusion limit of k/sub +/ and t/sub c/ when particles (LDL receptors) diffuse in two dimensions until they hit and are absorbed by circular absorbers (coated pits) that have finite lifetimes. The absorbers appear and disappear at equal rates so that their concentration remains constant. We use these expressions to show that a diffusion limit of k/sub +/ = 3 x 10/sup -10/ cm/sup 2//sec would be obtained if D, the diffusion coefficient for an LDL receptor on a human fibroblast at 37/sup 0/C equaled 3.3 x 10/sup -11/ cm/sup 2//sec. Because this value is in agreement with the experimentally determined value for D, we conclude that random insertion of LDL receptors into the plasma membrane, followed by pure diffusional motion of LDL receptors on the cell surface unti they are irreversibly absorbed in coated pits, is consistent with experiment.

• OSTI ID: 5301025
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 78:9
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
LIPOPROTEINS
RECEPTORS
BIOCHEMISTRY
CELL MEMBRANES
DIFFUSION
DIFFUSION COATINGS
FIBROBLASTS
PHAGOCYTOSIS
ANIMAL CELLS
CELL CONSTITUENTS
CHEMISTRY
COATINGS
CONNECTIVE TISSUE CELLS
LIPIDS
MEMBRANES
ORGANIC COMPOUNDS
PROTEINS
SOMATIC CELLS
550300* - Cytology
550200 - Biochemistry