What is claimed is:
1. A method for obtaining an isolated polynucleotide comprising a sequence encoding a protein having Rubisco activase activity, the method comprising:
recombining a plurality of parental polynucleotide species encoding at least one protein having Rubisco activase activity under conditions suitable for sequence shuffling to form a resultant library of sequence-shuffled polynucleotides;
transferring said library into a plurality of host cells, thereby forming a library of transformants wherein sequence-shuffled Rubisco activase polynucleotides are expressed;
identifying at least one transformant from said library that expresses a protein having a Rubisco activase activity that is significantly enhanced relative to the Rubisco activase activity of proteins encoded by the plurality of parental polynucleotide species, wherein the identified transformant contains a polynucleotide comprising a sequence encoding the protein having an enhanced Rubisco activase activity; thereby obtaining a polynucleotide comprising a sequence encoding the protein having an enhanced Rubisco acctivase activity.
2. The method of claim 1, wherein the encoded protein having an enhanced Rubisco activase activity has improved temperature stability relative to proteins encoded by the plurality of polynucleotide species.
3. The method of claim 1, wherein the encoded protein having an enhanced Rubisco activase activity has an higher temperature of optimum activity relative to proteins encoded by the plurality of polynucleotide species.
4. The method of claim 1, wherein the encoded protein having an enhanced Rubisco activase activity has significantly greater Rubisco activase activity relative to proteins encoded by the plurality of polynucleotide species.
5. The method of claim 1, wherein the encoded protein having an enhanced Rubisco activase activity has significantly greater ATPase activity relative to proteins encoded by the plurality of polynucleotide species.
6. The method of claim 1, wherein the step of identifying at least one transformant from said library that expresses a protein having a significantly enhanced.Rubisco activase activity comprises assaying for ATPase activity.
7. A method for expressing an enzyme having rubisco activity, the method comprising:
introducing a polynucleotide encoding an enzyme having rubisco activity into a chlamydomonas cell; and
culturing the chlamydomonas cell under conditions where the enyzme is expressed.
8. The method of claim 7, wherein the enzyme having rubisco activity is a Rubisco Form I L subunit.
9. The method of claim 7, wherein the enzyme having rubisco activity is a Rubisco Form I S subunit.
10. The method of claim 7, wherein the enzyme having rubisco activity is a Rubisco Form II subunit.
11. The method of claim 7, wherein the polynucleotide encoding an enzyme having rubisco activity is introduced into a nuclear genome of the chlamydomonas cell.
12. The method of claim 7, wherein the polynucleotide encoding an enzyme having rubisco activity is introduced into a chloroplast genome of the chlamydomonas cell.
13. The method of claim 11, comprising replacing a codon in the polynucleotide with a synonomous codon prior to introducing the polynucleotide into the chlamydomonas cell, wherein the codon replacement renders the codon usage of the polynucleotide more compatible with the chlamydomonas nuclear genome.
14. The method of claim 12, comprising replacing a codon in the polynucleotide with a synonomous codon prior to introducing the polynucleotide into the chlamydomonas cell, wherein the codon replacement renders the codon usage of the polynucleotide more compatible with the chlamydomonas chloroplast genome.
15. The method of claim 7, comprising modifying the intron usage in the polynucleotide prior to introducing the polynucleotide into the chlamydomonas cell.
16. The method of claim 15, wherein the intron usage in the polynucleotide is modified by removing an intron.
17. The method of claim 15, wherein the intron usage in the polynucleotide is modified by replacing an intron in the polynucleotide with an intron that occurs naturally in a chlamydomonas gene.
18. The method of claim 7, wherein the polynucleotide encodes a rubisco subunit derived from a eukaryote.
19. The method of claim 18, wherein the polynucleotide encodes a rubisco subunit derived from a higher plant.
20. The method of claim 19, wherein the polynucleotide encodes a shuffled variant of a rubisco subunit derived from a higher plant.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A constant velocity joint comprising:
an inner race;
inner engagement grooves each taking a circular arc in section and formed in a plurality of locations on an outer peripheral surface of said inner race in a direction right-angled to a circumferential direction;
an outer race provided along a periphery of said inner race;
outer engagement grooves each taking a circular arc in section and formed in positions facing to said inner engagement grooves on an inner peripheral surface of said outer race in the direction right-angled to the circumferential direction;
a cage sandwiched in between an outer peripheral surface of said inner race and an inner peripheral surface of said outer race and formed with pockets each elongated in a circumferential direction in positions aligned with said inner engagement groove and said outer engagement groove; and
a plurality of balls made capable of rolling along said inner engagement groove and said outer engagement groove in a state of being held inwardly of the pockets,
wherein an axial crossing angle between a central axis of said inner race and a central axis of said outer race is bisected,
said balls are disposed within a bisection plane orthogonal to a plane including these two central axes,
at least a part of said plurality of pockets are capable of holding said plurality of balls within said single pocket, and
a total number of balls is 7 or more.
2. A constant velocity joint according to claim 1, wherein the number of said pockets is even-numbered, and
the number of said balls held in each of said pockets is different.
3. A constant velocity joint according to claim 2, wherein the number of said pockets is 4,
the number of said balls is 10,
the number of said balls held in each of said two pockets existing on the opposite side in a diametrical direction is 2, and
the number of said balls held in each of said remaining two pockets is 3, respectively.
4. A constant velocity joint comprising:
an inner race;
inner engagement grooves each taking a circular arc in section and formed in a plurality of locations in a circumferential direction on an outer peripheral surface of said inner race in a direction right-angled to a circumferential direction;
an outer race provided along a periphery of said inner race;
outer engagement grooves each taking a circular arc in section and formed in positions facing to said inner engagement grooves on an inner peripheral surface of said outer race in the direction right-angled to the circumferential direction;
a cage sandwiched in between an outer peripheral surface of said inner race and an inner peripheral surface of said outer race and formed with a plurality of pockets each elongated in a circumferential direction in positions aligned with said inner engagement groove and said outer engagement groove; and
a plurality of balls made capable of rolling along said inner engagement groove and said outer engagement groove in a state of being held inwardly of the pockets, the number of said balls being the same as the number of said inner and outer engagement grooves,
wherein an axial crossing angle between a central axis of said inner race and a central axis of said outer race is bisected,
said balls are disposed within a bisection plane orthogonal to a plane including these two central axes, and
if a ratio Dcdm of a diameter Dc of the outer peripheral surface of said cage to a pitch circle diameter dm of each of said plurality of balls is set to R1, and if a ratio dcdm of a diameter dc of the inner peripheral surface of said cage to a pitch circle diameter dm is set to r1, there are relationships such as 1.06<R1<1.11, and 0.945<r1<0.998.
5. A constant velocity joint according to claim 4, wherein a ratio of a major diameter Da of said each ball to an average thickness tc of the cage which is expressed by of a difference between a diameter Dc of the outer peripheral surface of said cage and a diameter dc of the outer peripheral surface of said cage, has a relationship such as 0.16<rt<0.30.
6. A constant velocity joint comprising::
an inner race;
inner engagement grooves each taking a circular arc in section and formed in eight locations at an equal interval in a circumferential direction on an outer peripheral surface of said inner race in a direction right-angled to the circumferential direction;
an outer race provided along a periphery of said inner race;
outer engagement grooves each taking a circular arc in section and formed in positions facing to said inner engagement grooves on an inner peripheral surface of said outer race in the direction right-angled to the circumferential direction;
a cage sandwiched in between an outer peripheral surface of said inner race and an inner peripheral surface of said outer race and formed with eight pockets each elongated in a circumferential direction in positions aligned with said inner engagement groove and said outer engagement groove; and
eight pieces of balls made capable of rolling along said inner engagement groove and said outer engagement groove in a state of being singly held inwardly in each of the pockets,
wherein an axial crossing angle between a central axis of said inner race and a central axis of said outer race is bisected,
said balls are disposed within a bisection plane orthogonal to a plane including these two central axes, and
if a ratio tcDa is set to rt, there is satisfied a relationship such as:
(0.054rt)Daw(0.16rt)Da
where Da is the major diameter of said each ball, w is the circumference-directional width of each of the column members existing between the pockets adjacent to each other in the circumferential direction with respect to said cage, and tc is the diameter-directional thickness of each of the column members of said cage.
7. A rolling bearing unit for a wheel, comprising:
an outer race constructive member including respectively a first fitting flange, formed on an outer peripheral surface, for supporting said outer race constructive member on a suspension, and plural trains of outer race tranks formed on an inner peripheral surface, said outer race constructive member not rotating when used;
an inner race constructive member having the other side end portion formed as a housing unit serving as an outer race of a constant velocity joint, said inner race constructive member rotating when used;
a plurality of rolling members so provided as to be capable of rolling between said outer race tracks and said inner race tracks;
an inner race provided on an inner side of said housing unit and constituting said constant velocity joint;
outer engagement grooves each taking a circular arc in section and formed in a direction right-angled to a circumferential direction in a plurality of positions in the circumferential direction on an inner peripheral surface of said housing unit;
a plurality of inner engagement grooves each taking a circular arc in section and formed in the direction right-angled to the circumferential direction in positions facing to said outer engagement grooves on an outer peripheral surface of said inner race;
a cage sandwiched in between an outer peripheral surface of said inner race and an inner peripheral surface of said housing unit and formed with a plurality of pockets each elongated in the circumferential direction in positions aligned with said inner engagement grooves and said outer engagement grooves, said cage constituting said constant velocity joint; and
a plurality of balls so provided as to be capable of rolling along said inner engagement grooves and said outer engagement grooves between said outer engagement grooves and said inner engagement grooves in a state of being held inwardly of the pockets,
wherein an axial crossing angle between a central axis of said inner race and a central axis of said housing unit is bisected,
said balls constituting said constant velocity joint are disposed on a bisection plane orthogonal to a plane including these two central axes,
the number of said outer and inner engagement grooves and the number of the balls are each set to 7 or more,
a radius of curvature of each of sectional configurations of said two groups of outer and inner engagement grooves when cut off by an imaginary plane orthogonal to the central axis of said housing unit or of said inner race is made smaller at each of groove bottom areas of said two groups of outer and inner engagement grooves and made larger at both of side end portions proximal to respective opening edges, and
if a ratio d1d2 of d1 to d2 is set to R, there is a relationship such as:
0.49R0.63
where d1 is the pitch circle diameter of each of said balls constituting said constant velocity joint, and d2 is the pitch circle diameter of each of said rolling members constituting said inner rolling member train of said plurality of rolling member trains.
8. A rolling bearing unit for a wheel according to claim 7, wherein a sectional configuration of each of said two groups of outer and inner engagement grooves has a curvature radius larger than a curvature radius of the rolling surface of said each ball, and is formed of a pair of circular arcs meeting each other at the groove bottom area of each of said two groups of outer and inner engagement grooves, and
centers of the curvature radii of these circular arcs are offset each other in directions opposite to each other on the basis of the center of a grove width of each of said two groups of outer and inner engagement grooves.