Isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus Rana): changes during oocyte maturation |
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Authors: | Wang T Lessman C A |
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Institution: | (1) Department of Microbiology and Molecular Cell Sciences, The University of Memphis, 201 Life Sciences Building, Memphis, Tennessee 38152-3560 (USA), Fax +1 901 678 4457, e-mail: clessman@memphis.edu, US;(2) Present address: Cancer Center, Division of Radiation Oncology, Reed-Rose Gordon Facility, University of Massachusetts Medical School, 222 Maple Avenue North, Shrewsbury, Massachusetts 01545 (USA), US |
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Abstract: | Rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly
and disassembly dynamics of frog oocyte tubulin compared to that in brain. By using centrifugation, SDS-PAGE, two-dimensional
gel electrophoresis and Western blots, probed with anti-α-tubulin monoclonal antibodies, polymorphic α-tubulins (isoforms)
were compared in brains and follicle-enclosed oocytes of northern (Rana pipiens) and southern (R. berlandieri) frogs. Oocyte tubulin in both species had isoforms with greater ranges of isoelectric point (pI) than those of brain tubulins;
in particular, the oocyte tubulin pIs ranged further into the acidic region of the isoelectric-focusing gels than corresponding
brain tubulin. This difference may, in part, be responsible for the previously reported assembly differences between oocyte
tubulin (undetectable assembly) and brain tubulin (high assembly). Isoforms of α-tubulin with relat
ively acidic pI were more abundant in northern frog brain and oocyte soluble extracts than in analogous extracts from southern
frogs. Furthermore, additional acidic α-tubulin isoforms were found in progesterone-treated oocytes (i.e., eggs), indicating
increased heterogeneity of acidic a-tubulin isoforms during oocyte meiotic maturation. Among northern frog oocyte soluble
components fractionated on Superose-6b columns, tubulin complexes with apparent molecular mass of about 1800 kDa were found
to contain acidic α-tubulin isoforms while the putative oligomeric tubulins with an apparent molecular mass of about 250 kDa
contained an additional relatively basic α-tubulin isoform. The acidic α-tubulin isoforms, therefore, are proposed to be associated
with cold-adaptable cells of brain and oocytes, and may also be involved in stabilization of large soluble tubulin complexes
in oocytes of the northern frog.
Received 1 October 2002; accepted 9 October 2002
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ID="*"Corresponding author. |
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Keywords: | , Microtubule, SDS-PAGE, two-dimensional electrophoresis, isoelectric focusing, DM1A, species specificity, |
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