There are three structural forms of the natriuretic peptides (NP), designated as atrial NP (ANP), brain NP (BNP), and C-type NP (CNP). The amino acid sequence relationships for ANP (27 amino acids), BNP (32 amino acids), and CNP (22 amino acids) are illustrated in Figure 1A.

Fig1. Structural organization of the atrial natriuretic peptides, their receptors and their biological responses. (A) Amino acid sequences of ANP, BNP, and CNP. The translation of the three color codes for the atrial natriuretic peptides is as follows. The blue color represents the atrial natriuretic peptide (ANP) that is secreted by the human myocytes of the cardiac atrial portion of the heart; this is the reference peptide for the other amino acid sequences. The red color is the B-type natriuretic peptide (BNP) that is produced by both the human brain and the cardiac ventricles; the relative contributions of the two sources of BNP are not clear. The green color is the C-type natriuretic peptide (CNP). Each of the three natriuretic peptides is the product of a separate human gene transcript. The extent of the homology of the peptide sequences of BNP and CNP with the reference ANP can be judged by the position and number of the blue residues present in the red residues of BNP and in the green residues of CNP. Both BNP and CNP have precisely the same homology of 12–13 amino acid residues with ANP. Some evidence supports the view that BNP reduces ventricular fibrosis which is the abnormal thickening of heart valves. (B) Conversion of the linear amino acid sequences of ANP, BNP, and CNP into a circular structure created by a disulfide bond. All three natriuretic peptides are characterized by the presence of a 17-member amino acid ring formed by a disulfide bridge between two cysteine residues. (C) Ligand specificity of ANP, BNP, and CNP for binding to three classes of receptor. Schematic diagram of the interaction of atrial natriuretic peptide hormones binding to their receptors to generate initiation of biological responses. Panel C presents a schematic overview of the structural details of the three families of atrial natriuretic receptors. Both the NPR-A and NPR-B receptor proteins, but not the NPR-C receptor, are comprised of two identical receptor amino acid sequences (of 1037 amino acids) that are only covalently linked together inside the cell (see the blue and green boxes). The extracellular domains have 450 amino acid residues, a hydrophobic membrane spanning region (~21 amino acid residues), and an intracellular domain (566 amino acid residues). The intracellular portion of the receptor protein is divided into three distinct domains: (a) a 250 amino acid kinase homology domain (see blue ovals with several attached phosphates); (b) a 41 amino acid hinge-dimerization region; and (c) a 250 amino acid C-terminal guanylyl cyclase enzyme catalytic domain (see green boxes). In contrast, two NPR-C receptors form a dimer (via a disulfide bond) outside the cell. The NPR-C has a highly truncated intracellular peptide of only~80 amino acid residues and consequently has no catalytic guanylyl cyclase units. Definition of abbreviations: ANP, atrial natriuretic peptide; BNP, basic natriuretic peptide and/or brain natriuretic peptide; CNP, C-type natriuretic peptide; GFR, glomerular filtration rate; FF, fractional flow; UNaV, urinary sodium volume; UV, urinary volume; SNA, sympathetic nervous activity; VSM cell growth; vascular smooth muscle cell growth. (D) Atrial natriuretic hormones secreted by the heart and the wide sphere of action of their biological responses. ANP and BNP are true circulating hormones. They are released from the heart’s atria and ventricles into the circulatory system where they are taken up by the kidney. There are a variety of responses. These include inhibition of renin secretion, and also inhibition of the zona glomerulosa stimulating of aldosterone biosynthesis. ANP increases the glomerular f iltration rate as well as the amount of Na+ excretion in the urine. The capillaries experience an increase in permeability when exposed to ANP, thereby increasing the flow of blood. Abbreviations: FF, filtration fraction; GFR, glomerular filtration rate; SNA, sympathetic nervous activity; UNaV, urine sodium excretion; UV, urine volume, VSM, vascular smooth muscle. Abstracted from M.T. Rademaker & E. Espiner in The Endocrine Heart. In K.L. Becker, Ed.; Principles and Practice of Endocrinology and Metabolism, 3rd ed., Philadelphia 2001, Lippincott Williams & Wilkens.

All three natriuretic peptides are characterized by a 17-member amino acid ring formed by a disulfide bridge between two cysteine residues; see Figure 1B. Each of the three natriuretic peptides is the product of a separate gene and mRNA. The genes that code for ANP produce a prepro-ANP of 151 amino acids. Loss of the 25-amino-acid hydrophobic leader sequence generates a 126-amino-acid pro-ANP, which is stored in granules of the atrial myocytes. Mature ANP is generated at the time of secretion by cleavage of the pro ANP at Arg-98-Ser-99 to yield the mature peptide of 28 amino acid residues (residues #98–126 of pre pro-ANP) and the N-terminal peptide (residues #1–98 of prepro-ANP). The secretion of ANF is stimulated by any of the following: (a) atrial stretch caused by volume expansion; (b) elevated blood pressure; (c) atrial tachycardia; and (d) high-salt diet. BNP is secreted by the ventricles of the heart.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشؤون الفكريّة يُهدي إصداراته العلمية إلى مكتبات محافظة كركوك

شعبة فاطمة بنت أسد تطلق مسابقتها الإلكترونية (منارة الجود في مهد الصبا) لكتابة القصة للأطفال

المجمع العلمي يقيم برنامجًا قرآنيًا تعليميًا في النجف الأشرف

قسم الشؤون الدينية يقيم مجلسًا عزائيًّا لاستذكار أهل البيت (عليهم السلام)

المزيد

الآخبار الصحية

ما هي أفضل العصائر لصحة القلب وتقوية المناعة والنوم العميق؟

الأطعمة الغنية بالبروتينات النباتية تقلل خطر الأمراض المزمنة

وجع الأوتار قد يخفي خطرا صحيا مرتبطا بالقلب

أزمة "السفينة الموبوءة"..الأرجنتين تحقق في مصدر تفشي "هانتا"

المزيد

الآخبار التكنلوجية

باحثون يحددون تأثير القهوة على الميكروبيوم والمزاج

روسيا.. ابتكار تقنية لمعالجة سبائك التيتانيوم لحماية الطائرات والسيارات

بكين وواشنطن تدرسان إطلاق محادثات رسمية حول الذكاء الاصطناعي

لأول مرة في الولايات المتحدة.. تشغيل مفاعل مصغر نووي يغذي الذكاء الاصطناعي بالطاقة

المزيد

مواضيع ذات صلة

Hemoglobins with Increased Oxygen Affinity

Specific Enzymes are Associated with Compartments Separated by the Mitochondrial Membranes

ATP Acts as the “Energy Currency” of The Cell

Living Organisms Package Transition Metals Within Organometallic Complexes

Androgen Biosynthesis

Androgens and Related Molecules

Two-Dimensional Polyacrylamide Gel Electrophoresis

Isoelectric Focussing Gels

Native (Buffer) Gels

Sodium Dodecyl Sulfate (SDS)-Polyacrylamide Gel Electrophoresis

Transition Metals are Essential for Health

Individual Regulatory Events Combine to Form Sophisticated Control Networks