Microtubules, which play a part in moving parts of the cell from place to place, turn out to share a common ancestor with another protein which a key player in bacterial cell division in bacteria, and chloroplast division in plants. A similar protein has been found in the mitochondria of at least one alga.
The components of microtubules and the earlier proteins "are clearly related, judging from similarities in three-dimensional structure. And although the proteins share only about 15 percent amino acid sequence identity overall, they're much more similar at the local level, particularly at the domain responsible for binding and cleaving GTP."
This is only to be expected from evolution -- the sites that interact with other molecules will be more sensitive to changes, and amino acid sequences are expected to be conserved there. Changes away from these sensitive regions are less significant, as long as the overall shape of the protein remains the same.
Actin is another essential component of the eukaryotic cytoskeleton--a globular protein that binds nucleotide, in this case ATP. In the cell, it cleaves ATP into ADP and phosphate. (It is also a major component of muscle tissue, forming part of the machinery that allows muscle fibers to contract.)
Actin turns out to be related to a whole family of proteins, including one which is involved in glycolysis, the basic metabolic process in anaerobic life. Another related protein generates and maintains the rod shape of bacilli. Structural similarities hint that actin is more closely related to the bacterium Thermotoga maritima, and may share a common ancestor with the protein in that bacterium.
Interestingly enough, we have many sets of protein which are very similar in shape and function, but which differ more than a little in the details of their composition. The differences that turn up are orderly enough to look like family resemblances, and can seem to indicate a family of descendants of a common ancestor. Again, evolution would predict this sort of distribution. One member of the family was incorporated into eukaryotic cells, and its protein was passed down to all its descendants. Other members of that ancestral family were already slightly different from the ancestor of eukaryotes, and to these differences were added other mutational changes.
The protein in the nearest relative, Thermotoha maritima, has slight differences from modern actin because, although the ancestral bacillus protein and the ancestral actin were once identical twins, they have diverged through random mutations.
When scientists investigate the intricate molecular machinery in cells, they find that these machines, rather than springing up fully-formed out of nowhere, there are numerous relatives and precursors in other organisms, and sometimes in the same cell. The development of cellular machinery is not so much an account of complicated machinery appearing out of nowhere, but more of existing bits and pieces being fitted together to solve different problems.
And once again, pay particular notice to how evolution is treated in this article. It is in no way a sense of "Hey, guys! It happened!". Instead, it's a matter of, "We've been pretty darn sure it happened; this is how it happened in this case." The only people caught up in whether evolution can be "proven" seem to be the Intelligent Design / Intelligent Origin crowd and the Creationists.
Osteryoung states unequivocally that these eukaryotes descended from prokaryotes. Yet there is no proof of this contained in the article, which only points to certain protein similarities. "Looks like" is not the same thing as "comes from."
Notice the tacit assumption? The very first sentence of the article does not ponder whether this occured or how it might have occured, but takes it as a given, the only task being how to demonstrate the mechanism.
The very next paragraph demonstrates the same confusion between what has been demonstrated and what has merely been theorized. The author even admits that the "evolution" of the chloroplast only "most likely" from the ana-protobacterium. Doesn't sound like much of an "answer" to me. Sounds more like theory or conjecture being represented as a settled matter.
Of course, Earth just happened to be in the right location and distance from the Sun; geologic processes just happened to be in the correct sequence; just the right amount of "star matter" and radiation was allowed to fall upon proto-Earth; just the right amount and mixtures of chemical "soup" happened to occur on Earth. ad nauseum.
Yes, it all happened just right and "POOF!" Life, as we 'know' it............evolved!
WOW!
No where else(?) can evolved sentient creatures ponder their own existence and "creation".
It's freaking amazing, eh?
Why provide a number when it shows a difference and only a vague "much more" when the similarity is purported to be important? It seems to me that the number, if significant should be at least 30%, given my interpretation of much and the general chimp/human genome simularity of ~98%. (it also matters as to the definition of local)
So, why is it that an infinitely more complicated pattern and structure in biology must have happened by chance?
Evolution, while claiming to be intellectual and logical, seems very illogical to me.
So we can say now that two proteins must be related because they share a similar function in one domain and they have a whopping 15% homology!
I've done a little study of my own. I found that a yugo shares many of the same functions as a Honda Civic. They both have four wheels, a motor, a steering wheel, a gas pedal, a brake, headlights, etc. In fact, I'm sure that they share more than a 15% homology.
I have concluded that long ago, a steel mill blew up and over billions of years, yugos evolved. After another billion years, Honda Civics have evolved from yugos. If we carry this evolution even farther, we get a Hummer!
All organisms share some sort of homology. If one function is to be performed (like the cleaving of GTP), it would make sense that God used a very similar-looking molecule to accomplish the task.
The development of cellular machinery is not so much an account of complicated machinery appearing out of nowhere, but more of existing bits and pieces being fitted together to solve different problems.
While this article discusses protein similarities, the question still remains: what is the MECHANISM of the change? How long did it take? Is anyone in control of it? I believe that God has taken these bits and pieces and put them together to create distinct organisms. These organisms all share the same building blocks and need to perform some of the same functions, so of course some of the molecules will look similar. This is analagous to the car example. A Honda Civic shares a lot of the same parts with a Honda Accord. It does not mean one "evolved" from the other, it means they had the same DESIGNER!
Think about it. If God didn't design this world and its inhabitants so that they would be somewhat similar, it wouldn't function the way it does. Just because things have similarities does not mean that they were not designed that way on purpose. If God didn't use the same 20 amino acids to make up all the proteins in this world, we wouldn't be able to eat anything.
The design of this world is so intricate and ingenious that I am in awe. I can't reconcile the word "accident" with the things I see happening in the human body, let alone the interworkings of the world with its inhabitants and the inhabitants with each other.
I'm for hypothetically dissecting the mysteries of origins as far as possible, and yet I still wish to hold the mystery of creation dearly. Panspermia is a worthy contender, as is the quantum multiverse concept, at least to my ways of thinking at this time.