Macronutrients
Chuong Pham-Huy, Bruno Pham Huy in Food and Lifestyle in Health and Disease, 2022
Proteins are polymers of different amino acids linked together by peptide bonds in the form of long filaments (polypeptide chains). They wrap themselves in a virtually infinite number of spherical or helical forms, which explains the wide variety of functions performed by proteins (36–38, 47). Proteins differ widely in amino acid content. Some amino acids which are in abundance in one protein may be in meagre amounts in others, and may even be lacking in the rest. Tryptophan, for instance, lacks in certain proteins. However, most of the proteins in animal and plant foods contain all the 20 amino acids (36, 38, 47). The proportion of these amino acids varies as a characteristic of a given protein, but all food proteins contain some of each. Collagen, a fibrillar protein that acts like glue between cells, consists of more than one thousand amino acids. Titin or connectin is a giant protein, greater than one µm in length, the largest known protein. It accounts for the passive elasticity of muscles, and consists of more than 25,000 amino acids (1). Titin is known as the largest sarcomeric protein that resides within the heart muscle. Mutations in the titin gene can cause cardiomyopathies, in particular, dilated cardiomyopathy (48). This cardiac disease is characterized by systolic dysfunction and dilation of the left ventricle (48).
Finding a Target
Nathan Keighley in Miraculous Medicines and the Chemistry of Drug Design, 2020
Proteins have three-dimensional folded structures; the shape of which is very specific, depending on the almost infinite variety of amino acid sequences, and is predetermining for their given function. Proteins can fold into a regularly repeating secondary structure; either an α-helix or a β-pleated sheet. These structures are governed by the primary structure; as hydrogen bonds are formed between different amino acids in the chain, or covalent bonds in disulphide bridges between cysteines. In an α-helix, the primary chain twists into a coil about a central axis, while an undulating sheet-like structure is obtained in the formation of a β-sheet: which of these different structures is formed depends on the precise hydrogen bonding that arises from the given sequence of amino acids. Further folding may then occur to produce a tertiary structure. For proteins composed of several constituent polypeptide chains, the final folded structure is referred to as the quaternary structure. These unique shapes have discrete implications regarding the function of the protein.
Conditioning of Hair
Dale H. Johnson in Hair and Hair Care, 2018
b. Proteins. Proteins serve many diverse biological functions acting as catalysts in enzymes, structural elements in bone collagen and hair keratin, nutrient storehouses in milk casein and egg ovalbumin, and many more. Proteins are made up of one or more polypeptide chains which in turn are made up of many alpha-amino acid residues linked together by a peptide bond. There are 20 different alpha-amino acids commonly found in proteins (42), listed in Table 2. All of these amino acids, except for proline, contain a free carboxyl group and a free unsubstituted amino group on the alpha-carbon. The amino acids differ from one another by their side chain R groups. Many amino acid residues are arranged in complex specific sequences to form proteins which range in molecular weight from about 5000 to over 1 million.
Ribosomopathies and cancer: pharmacological implications
Published in Expert Review of Clinical Pharmacology, 2022
Gazmend Temaj, Sarmistha Saha, Shpend Dragusha, Valon Ejupi, Brigitta Buttari, Elisabetta Profumo, Lule Beqa, Luciano Saso
Ribosomes are ribonucleoprotein complexes discovered by Palade and Porter in 1954 as small round bodies associated with the endoplasmic reticulum (ER), as observed using an electronic microscope [1]. It is well known that genetic information is stored in deoxyribonucleic acid (DNA) molecules, and by the highly regulated mechanism of transcription, genes, as particular segments of DNA, are copied into mRNA (ribonucleic acid) by the RNA polymerase enzyme. Ribosome macromolecules catalyze the translation of information from mRNAs into functional polypeptide chains. Ribosomes consist of large and small subunits. Eukaryotic ribosome consists of a smaller 40S subunit and a large 60S subunit. The smaller 40S subunit consists of 18S ribosomal RNA (rRNA) and 33 ribosomal protein small (RPS) subunits, whereas the 60S subunit contains 28S, 5S, and 5.8S rRNA and 47 ribosomal protein large (RPL) [2,3].
The nanotechnological approach for nasal delivery of peptide drugs: a comprehensive review
Published in Journal of Microencapsulation, 2022
Carine Zuglianello, Elenara Lemos-Senna
Peptides are biomolecules found in all living organisms and play a key role in all manner of biological activities. Structurally, peptides are made of chains from 2 to 50 amino acids that are held together by peptide bonds (–CONH–). Meanwhile, polypeptides and proteins are made of over 50 amino acids held in a single chain or assemblies of two or more chains, respectively. In the human body, peptides are found in every cell and tissue and perform a wide range of essential functions. Maintenance of proper concentration and activity levels of peptides is necessary to achieve homeostasis and keep health. Currently, there is an increased interest in peptides in pharmaceutical research and development. Peptide drugs are recognised for having high selectivity and therapeutic efficacy being, at the same time, safe and well tolerated. Higher ordered peptide structures with defined chemistry are capable of cellular targeting, recognition, and internalisation (Edwards and LaPlante 2011, Bhatia 2017, Sachdeva 2017).
Antimicrobial peptides and other peptide-like therapeutics as promising candidates to combat SARS-CoV-2
Published in Expert Review of Anti-infective Therapy, 2021
Masoumeh Sadat Mousavi Maleki, Mosayeb Rostamian, Hamid Madanchi
Transferrins are iron-binding proteins with antiviral activity. The most well-known transferrin is lactoferrin (LF), which is a multifunctional 80-kDa glycoprotein and is widely available in various secretory fluids. LF, first discovered in cow’s milk, is evolutionarily highly conserved and is found in humans, mice, and pigs. Its structure consists of a polypeptide chain that has a positively charged N-terminal region. The LF chain has two circular loops connected to three spiral α-helixes, each of which has an iron-binding site. There is a strong connection between two loops when iron binds (the holo-form), which makes LF resistant to proteolysis [40]. Reports have indicated that bovine lactoferrin is a potent inhibitor of a broad number of viruses and has higher antiviral effects than human lactoferrin. Lactoferrin specifically binds to the subunit A2 of the hemagglutinin and inhibits influenza virus infection and related hemagglutination [63]. Lactoferrin has been shown to inhibit infection by binding to adenovirus III and IIIa structural polypeptides targets [64]. The inhibitory effect of LF on DENV [65], Marek’s Disease Virus (MDV) [66], and HCV [67] has been investigated. Recent studies showed that LF can interfere with some of the receptors involved in SARS-CoV-2 pathogenesis and also prevents the entering of the virus via ACE2 to host cells [68]. Therefore, LF may contribute to the prevention and treatment of COVID-19 [68].