Is Pentax K series lens compatible with Nikon DSLRs?

I have a nearly 3 decade old Pentax ME model SLR
It has a K series joint which locks the lens with the body
I wish to ask, can the Kseries Lens be fitted on a F series DSLR body which is mostly found in NIKON?
If no, then what is the difference between them?

All DSLR manufactures use different mounts. Nikon, Canon, Sony, Pentax ex all use different mounts. They all differ in the way the lens fits to the body. The Attachment points are all different and also with today's lenses with CPU's the lens will communicate with the body differently. If you look on e-bay they do sell adapters that will allow manual lenses to from different makes to work on your pentax. The same is true for Nikon and Canon. Just note that you won't have control over aperture with modern lenses or Auto focus with any lens.

Various adapters exist, but a search for adapter Pentax Nikon at BH Photo failed to show a Pentax K lens to Nikon F body.
http://www.bhphotovideo.com/...av-Search=
The Pentax K lenses could probably find a buyer, although not at a great price. I think they can fit Pentax DSLR's, although with nothing electronically connected or automatic, newer lenses would be more attractive. There are still some users of older Pentax film SLR's. The Promaster 2500PK Super is a currently manufactured film camera that could use them. If the Pentax ME is still working, bundling it with your Pentax K lens collection you could possibly find a buyer, although it won't fetch you a lot of money.

All camera manufacturers use a proprietary lens mount and there's NO compatibility between different brands. If you have several Pentax lenses then buy a Pentax K-30 and those older lenses will be right at home on it.

Although you might be able to find a Pentax "K" to Nikon "F" adapter, unless you have a really exotic Pentax lens you'll find adapters are more trouble than they're worth. Infinity focus may not be possible, you'll have to use stop-down metering and of course you'll have to manually focus the lens.

NOTE: Using any manual focus lens on a modern DSLR requires manual focusing but at least using a Pentax manual focus lens on a Pentax DSLR allows infinity focus and in some instances Aperture Priority metering. Plus since Pentax has their version of image stabilization in the camera body any lens used becomes a stabilized lens.

So if you already have a Nikon DSLR I suggest selling your Pentax ME and Pentax lenses and using the money for Nikon lenses.