Nov. 27, 2017
Our immune systems include a long list of defenses ready to stop pathogens every step of the way. The very first of these defenses is the outer layer of our skin called the epidermis. The epidermis is made of specialized cells called keratinocytes specifically named because they produce a structural protein called keratin en mass. The life of keratinocytes is really quite interesting! Keratinocytes start their lives as epidermal stem cells and randomly become a short-lived progenitor called a “transit amplifying cell”. This cell type continues to divide and migrate towards the outer layer of the epidermis. Along the way, the cell differentiates a few times and takes on new behaviors and characteristics. The final stage of the keratinocyte is the corneocyte. This cell is characterized by exiting the cell cycle, losing its nucleus and cytoplasmic organelles, and having its plasma membrane replaced with a host of keratin-proteins. This new keratin membrane is enveloped by an insoluble amalgam of proteins and linked by transglutamines and lipids. That’s the skin you see and touch! It’s made of proteins and fats. In fact, keratin forms a whole list of structures including hair, nails, hooves, feathers, horns, etc. which distinguish themselves by amount and type of keratin produced. There are dozens of different types of keratin, but each are structurally quite similar as you can see from the picture which includes keratins 1 and 10. Info about differentiation from: https://www.proteinatlas.org/humanproteome/skin
Nov. 20, 2017
What makes cells grow? Growth factors are any of a group of proteins that stimulate the growth of specific tissues. They play an important role in promoting cellular differentiation and cell division. They bind to receptors on the cell surface, with the result of activating cellular proliferation and/or differentiation. Growth factors are quite versatile, stimulating cellular division in numerous different cell types; while others are specific to a particular cell-type. The loss of or decreased requirement for specific growth factors is a common occurrence in neoplastically transformed cells and may lead to a growth advantage, a cardinal feature of cancer cells. Recent work with transforming growth factors, the platelet-derived growth factor, and oncogenes has produced some insight into the mechanisms through which alterations in growth factor-receptor-response pathways could lead to a growth advantage. PDB: 4QCI is a blocking Anti-Platelet-Derived Growth Factor (PDGF) monoclonal antibody
Oct. 23, 2017
Myoglobin is a small protein which stores oxygen for your muscle cells to use when they need it most. It contains a special disk-shaped molecule called heme, which has a perfectly sized hole in its center that lets it hold an oxygen molecule for later use by the cell. Myoglobin is important for muscular function, but it is a special molecule in structural biology for a different reason altogether: myoglobin was the first molecule to ever have its structure determined by x-ray crystallography! John Kendrew won the 1962 Nobel Prize for his structure of myoglobin, and laid the foundations for thousands of structural biologists to follow in his footsteps. By 1982, the Protein Data Bank already contained 100 such structures, and in 2014, it surpassed 100,000! Structural biology has really come a long way in the past sixty years, and it all started with myoglobin.
Oct. 16, 2017
Penicillin is a broad-spectrum antibacterial drug, but few of us have considered how this drug performs its primary function. Essentially, penicillin reduces the integrity of bacterial cell walls. Bacteria are constantly replenishing their cell walls when growing or reproducing much like we regenerate our skin. Expansion is accomplished via a network of enzymes and peptidoglycans, the cell wall “bricks”. Penicillin-binding proteins (PBP) belong to a subgroup of enzymes called transpeptidases and are the essential “brick-layers” for bacteria. PBPs catalyze the reaction between peptidoglycans by mediating the removal of D-alanine from the precursor of peptidoglycan. This results in a conformational change and binding of adjacent peptidoglycans. Penicillin acts as an inhibitor for this reaction. The structure of penicillin is very similar to that of the peptidoglycans, so PBP forms a bond with penicillin at the active site. In fact, it’s a covalent bond, so it’s irreversible! PBP is thence rendered inactive, peptidoglycans are left unlinked, and the bacterium’s cell wall is full of holes. Osmotic pressure builds on the bacterium as the cell wall further degrades and eventually leads to cell death. Better them than you! PBPs come in a variety. Pictured here is Penicillin-binding Protein 2a from a resistant strain of Staphylococcus Aureus strain 27r. This bacteria evolved a mutation which allows its PBP2a to resist binding to penicillin. PDB: 1VQQ
Oct. 9, 2017
With all the fresh water generated by hurricanes such as Harvey uncommon infections in the USA such as Schistosomiasis, also known as bilharzia or “snail fever” can be a worry for victims of the hurricane as well as for volunteers. The infection is a parasitic disease carried by fresh water snails infected with one of the five varieties of the parasite Schistosoma. Found predominantly in tropical and sub-tropical climates, schistosomiasis infects 240 million people in as many as 78 countries, with a vast majority of the burden occurring in Africa. Schistosomiasis ranks second only to malaria as the most common parasitic disease. Schistosomiasis is transmitted by contact with contaminated fresh water (lakes and ponds, rivers, dams) inhabited by snails carrying the parasite. Swimming, bathing, fishing can put people at risk of contracting the disease. PDBID: 5fue is the Crystal structure of Schistosoma mansoni HDAC8 complexed with 3- benzamido-benzohydroxamate
Oct. 2, 2017
New Delhi Metallo-beta-lactamase-1 (NDM-1) is an enzyme responsible for bacterial resistance to broad-spectrum antibiotics. These antibiotics share a common structure of a beta lactam ring which is susceptible to degradation by NDM-1. Misuse of antibiotics can increase drug resistance of bacteria, resulting in future infections that can become extremely difficult to treat.