The role of renin binding protein (RnBP) in human (patho)physiology, despite its biochemical characterization, is as yet unclear. RnBP has been shown to bind and inactivate renin, a key player of the blood pressure regulating renin-angiotensin system. This renders the RnBP gene a promising candidate gene in human hypertension. Herein, a molecular genetic approach was employed to investigate if RnBP might affect renin, prorenin and/or blood pressure levels. Sequencing of the human Xq28 chromosomal region provided the precise chromosomal location and full genomic sequence of the RnBP gene. All 11 exons, adjacent intronic splice sites and the promoter region were sequenced in 20 patients with essential hypertension of early onset and possible X-linked inheritance and in four normotensive individuals. The only variant found was a single base exchange polymorphism 61 base pairs upstream of the intron 6/exon 7 boundary (T61C). Several cardiovascular parameters, the renin, and prorenin levels and the T61C allele status were determined in 505 Caucasian individuals. Male individuals without medication who were hemizygous for the C allele were characterized by lower prorenin levels (196 +/- 15 versus 256 +/- 12 mU/l, P = 0.05) and a significantly higher renin/prorenin ratio (10.7 +/- 1.5 versus 7.7 +/- 0.3%, P = 0.002), whereas no variations in circulating renin, blood pressure, heart rate and left ventricular mass index were associated with the C allele. No significant association was observed in women. The data do not exclude a role of RnBP in essential hypertension. The complete genomic structure of the RnBP gene, including the identified repetitive sequence elements, provides an essential tool for further studies of the RnBP gene in hypertensive patients with a different genetic background.