Evolution of complexity in molecular “machines”

V-ATPase proton pump and evolutionary pathway

A proton pump is a ring of proteins embedded in a cell wall, which moves molecules, atoms, or ions through the wall in a preferred direction. Research into the V-ATPase proton pump in eukaryotes has a ring of  six linked protein molecules in the membrane wall and a ring of eight inside the cell. As its name implies, it moves hydrogen ions (protons), through the cell wall. Research into its history shows that greater complexity can evolve without a change in function. The “V” indicates a plant vacuolar pump. They are found not in the external cell wall but in the walls of vacuoles, or liquid-filled spaces, within the cell.

…the complexity of an essential molecular machine—the hexameric transmembrane ring of the eukaryotic V-ATPase proton pump—increased hundreds of millions of years ago. We show that the ring of Fungi, which is composed of three paralogous proteins, evolved from a more ancient two-paralogue complex because of a gene duplication that was followed by loss in each daughter copy of specific interfaces by which it interacts with other ring proteins. These losses were complementary, so both copies became obligate components with restricted spatial roles in the complex. Reintroducing a single historical mutation from each paralogue lineage into the resurrected ancestral proteins is sufficient to recapitulate their asymmetric degeneration and trigger the requirement for the more elaborate three-component ring. Our experiments show that increased complexity in an essential molecular machine evolved because of simple, high-probability evolutionary processes, without the apparent evolution of novel functions. They point to a plausible mechanism for the evolution of complexity in other multi-paralogue protein complexes.

“Evolution of increased complexity in a molecular machine,” Gregory C. Finnigan, Victor Hanson-Smith, Tom H. Stevens & Joseph W. Thornton. Nature (2012). doi:10.1038/nature10724.

I won’t be able to give a detailed explanation until the description comes out from behind a paywall. There’s an explanation at Nature blog and one at  Kurzweil.

Look here for a diagram of V-ATPase. This diagram shows the ancestral molecule, in green, and its more specialized descendents, which need their increased complexity to properly assemble and function. The ancestor is on the left.

Evolution of V-ATPase protein chains

Lesbian families are better for children

I should have mentioned this research before, but Rick “Frothy Feces” Santorum has motivated me by claiming the lie that a gay father is worse for children than a father in prison. Hasn’t he seen the studies? The American Academy of Pediatrics recommended that same-sex marriage be legalized for the good of the children. He should read the long-term research study showing that children of lesbian households are better adjusted (possible confounding factors: planned pregnancies, lots of joint custody) than of mixed-sex households, with superior marks, self-esteem, and behaviour. Then he should read the study that reported ZERO INCIDENCE of child abuse in lesbian households—if he does read, that is.

Furthermore, same-sex marriages are no worse for children than mixed-sex marriages. From the paper by the American Academy of Pediatrics comes a virtual roll call of America’s psychiatric associations endorsing gay adoption, gay civil unions, and gay marriage:

• A growing body of scientific literature demonstrates that children who grow up with 1 or 2 gay and/or lesbian parents fare as well in emotional, cognitive, social, and sexual functioning as do children whose parents are heterosexual. —American Academy of Pediatrics, Committee on Psychosocial Aspects of Child and Family Health, 2002
• Children who are born to or adopted by 1 member of a same-sex couple deserve the security of 2 legally recognized parents. —American Academy of Pediatrics, 2002
• The National Association of Social Workers (NASW) “encourages the adoption of laws that recognize inheritance, insurance, same-sex marriage, child custody, property, and other relationship rights for lesbians, gay, and bisexual people. NASW supports the adoption of local, state, federal and international policies/legislation that protect the rights and well-being of the children of lesbian, gay, and bisexual people.” (2005)
• The American Medical Association (AMA) House of Delegates overwhelmingly endorsed a policy that calls on the AMA to “support legislation and other efforts to allow adoption of a child by the same-sex partner or an opposite-sex non-married partner who functions as a second parent or co-parent to that child.” (2005)
• The American Psychological Association (APA) adopted resolutions stating that “the APA believes that it is unfair and discriminatory to deny same-sex couples legal access to civil marriage and to all its attendant benefits, rights, and privileges … and shall take a leadership role in opposing all discrimination in legal benefits, rights, and privileges against same-sex couples.” (2005)
• The American Academy of Family Physicians’ Congress of Delegates agreed to “establish policy and be supportive of legislation which promotes a safe and nurturing environment, including psychological and legal security, for all children, including those of adoptive parents, regardless of the parents’ sexual orientation.” (2006)
• The American Psychoanalytic Association position states, “Accumulated evidence suggests the best interest of the child requires attachment to committed, nurturing and competent parents. Evaluation of an individual or couple for these parental qualities should be determined without prejudice regarding sexual orientation. Gay and lesbian individuals and couples are capable of meeting the best interest of the child and should be afforded the same rights and should accept the same responsibilities as heterosexual parents.” (2006)
• There is no evidence to suggest or support that parents with a gay, lesbian, or bisexual orientation are per se different from or deficient in parenting skills, child-centered concerns and parent-child attachments, when compared with parents with a heterosexual orientation. It has long been established that a homosexual orientation is not related to psychopathology, and there is no basis on which to assume that a parental homosexual orientation will increase likelihood of or induce a homosexual orientation in the child. Outcome studies of children raised by parents with a homosexual or bisexual orientation, when compared with heterosexual parents, show no greater degree of instability in the parental relationship or developmental dysfunction in children. The AACAP opposes any discrimination based on sexual orientation against individuals in regard to their rights as custodial or adoptive parents.” —American Academy of Child and Adolescent Psychiatry (AACAP)