Reference "Localization of free and bound biotin in cells from green pea leaves"

Reference ID

54994

Title

Localization of free and bound biotin in cells from green pea leaves

Source

Arch Biochem Biophys, 1993, vol. 303, pp. 67-73

Authors (4)

Baldet-P	Alban-C
Axiotis-S	Douce-R

Abstract

Cytosol and vacuoles from protoplasts, chloroplasts, and mitochondria from green
pea (Pisum sativum) leaves were purified and examined for their biotin content.
The bulk of free biotin was shown to be exclusively associated with the
cytosolic fraction at a concentration of about 4 pmol/mg protein and no bound
biotin was detected. The bulk of bound biotin (biotin-containing carboxylases)
was associated with the soluble fraction of chloroplasts and mitochondria at a
concentration of about 1.2 and 13 microM, respectively. No free biotin was
detected in these organelles. Western blot analysis of total, chloroplastic, and
mitochondrial polypeptides, using horseradish peroxidase-labeled streptavidin,
revealed three biotin-containing polypeptides with molecular mass of 220,000,
76,000 and 34,000. All were detected in the total pea leaf extract, but the M(r)
76,000 and the M(r) 34,000 biotinylated polypeptides were only detected in
mitochondria and chloroplasts, respectively. 3-Methylcrotonyl-coenzyme A
carboxylase and acetyl-coenzyme A carboxylase activities were measured in these
two compartments, respectively. Previously, it has been shown that the M(r)
76,000 polypeptide was the biotinylated subunit of the mitochondrial 3-methylcrotonyl-
coenzyme A carboxylase. In this paper, the origin and putative function of free
biotin located in cytosol are discussed.