Sulfur vulcanizes liquid latex into rubber shapes and sulfur does the same for structural and working proteins.  That sulfur is part of the 3-carbon cysteine, made from the 4-carbon homocysteine, itself only made from the 5-carbon essential amino acid methionine [thio means sulfur, meth means a 1-carbon atom group like methane, natural gas, and -ine stands for protein, nitrogen or amino, like ammonia].

Requiring most B-vitamins, the '4' is recycled back into methionine or turned into 3-carbon cysteine.  Homocysteine is even more toxic when it forms a high-energy 'Evil Ring', a 'Lethal Lactone' looking for proteins to corrode with its sulfur and oxygen, opening at x-x in the picture.  If homocysteine would 'thiolate' a protein that lives about 1 hour like insulin, with 6 cysteines forming 3 sulfur 'bridges', we'd simply make new.   When it corrodes the protein of LDL-cholesterol droplets that lives 2.5 days, things get serious.  Homocysteine makes it a Trojan horse and affects its function.  However, if corrosion is to a life-long protein with 380 cysteines like micro-fiber fibrillin, the damage can be artery fatal, as in Marfan syndrome and homo-cysteine-uria.

Because 'straight' homocysteine can fold back onto itself, if it would wind up in a protein during synthesis it could cleave the protein.  Thus, it is removed .. but in that reactive ring shape --doing damage 'thiolating' the cell and surrounding structure.

So, what's to corrode in an artery?

Well, I like to think of arteries as a thick multi-layer of muscle cells sandwiched between 2 structural layers.  Through the outside layer come 300 capillaries per square millimeter feeding the central muscle cells.  On the inside is a cell-hostile layer of just structure.  There are basically 3 materials: collagen, elastin with its fibers (about 18, all proteins) and proteo-glycans (stuff also found in cartilage).  Here it gets interesting.  Some of these 3 structural families can be life-long and all are corroded, poorly made or poorly repaired in the presence of that 'Evil sulfur ring'.  The 3 structural families are:

  1. Collagen, bundles of 3-strand rope stronger than nylon of which the ends during assembly are kept from unraveling by cysteine sulfur 'bridges'.  The ropes are then interconnected by 3-armed pyridinoline (see picture) that cannot be made when homocysteine has destroyed the machine (lysyl-oxidase) making this 'glue'.  Copper and vitamins B6 and C are also essential.  In bone, calcium builds along this rope, in artery the rope keeps it from ballooning under pressure.  Collagen without shape is gelatin.

   2. Elastin, an amazing 'rubber' NOT vulcanized by sulfur but by the above mentioned lysyl-oxidase but that, here, in elastin, forms 4-armed 'desmosine' cross-links.  Again: high homocysteine, insufficient copper or vitamins B6 (most people) or C, no bridges.  This stuff is so tough, it survives a week-long bath in hot acid or alkaline.  It is secreted and then assembled into life-long 'apartments' by the fragile muscle cells, protecting them in multi layer (laminae) rooms with windows (fenestrations) and elastin frames and curtains.  Without such 'happy homes' muscle cells may wander into the inside layer of the artery where they [and the artery owner] come to grief.  While collagen may live for years (less than 1 year in heart), elastin's half-life is an astounding 70 years. The bad news is that the other half has to be maintained, or made anew.    

   3. Proteo-glycans, a family of water filled 'compressive' and 'chemical storage' molecules of arteries and joint cartilage.  It has 'di-cysteine' sulfur bridges in a 'core-protein', and bottle brush like arms made from glucosamine and chondroitin sulfates.  That is the stuff that works for joint pain and repair.  Homo-cysteine can damage the protein and add excess sulfate to the glycan (sugar-like) arms, affecting function and making it attract LDL droplets that should not be there.

Lowering homo-cysteine

When methionine donates its 1-carbon methyl group [-CH3] to one of about 100 enzymes (protein machines), it turns into that temporary toxin.  Strategies :

First, eat foods with methyls, like eggs, liver, soybean lecithin and foods with betaine (tri-methyl-glycine, TMG) such as wheat bran, germ and spinach.  Eating such 'high choline' foods (including beans, rice, peas, lentils) we don't spend methyl from methionine needed for more vital roles.  Insufficient (B-vitamin regenerated) methionine and your DNA looks like if radiated by X-rays, says Bruce Ames.  Moreover, think cancer, all kinds of birth defects including, severe heart defects.

Second, subtract one carbon to make cysteine for which many of us need 3 to 15x more vitamin B-6 than average intakes, or about 5 - 25 mg/d.  No B-6 and atherosclerosis is quick and massive (picture).  Alternatively, add one carbon to re-generate methionine with betaine (see above; 2-5 g/day) or with vitamin B12 plus folic acid and here, without both, nothing happens and homocysteine sky rockets. Magnesium, copper, zinc and vitamin B2 also help reduce corrosive homocysteine.  Sadly, the best 'well balanced' diet has insufficient amounts of most actors.

Third, coffee (sorry), smoking, mental stress, high-dose niacin (to raise the 'happy' HDL-cholesterol) and drugs like fibrate and methotrexate raise homocysteine.  In each case a multi-vitamin as described here reverses that corrosive increase.

Know your homo-cysteine

Most heart disease, stroke, macular degeneration, cancer, Alzheimer's, joint and bone disease (fracture) does not happen when keeping your life-long homocysteine near SIX [6 µmol/L].  This theory of healthy aging unites all roads of research.  When all road signs read Rome, it may be wise to heed their advice.  When your car or proteins are damaged by corrosion, can a 'car'diologist, blood pressure or cholesterol drug really restore youth?